"Nine companies that build custom AI voice agents, compared by what each one builds, the platforms its own page names and who it suits, with sourced 2026 build ranges and the FCC rule on AI voices."
Key Takeaways
- 1Nine firms that build custom AI voice agents, read on their own sites on 29 October 2026: Appinventiv, Appther, Concret.io, FactoryJet, Groovy Web, Intellectyx, Master of Code Global, RaftLabs and Softcery.
- 2A development firm builds the agent around your calls and systems. A platform such as Retell AI or Vapi needs your own developer. A ready-made AI receptionist needs neither.
- 3Published build ranges run from $3,000 to $12,000 for a single-purpose agent (Groovy Web) up to $150,000 to $300,000+ for enterprise-grade work (Master of Code Global).
- 4Since 8 February 2024 the FCC treats AI-generated voices as "artificial" under the Telephone Consumer Protection Act (TCPA), so outbound voice agents need robocall-grade consent.
- 5Test every builder on your own call recordings: latency, the hand-off to a person, consent handling and the write-back to your CRM.
The best AI voice agent development company is the one that can play your own call recordings through a working agent, pass a caller to a person with notes attached and write the result into your CRM. Nine firms that build custom voice agents are compared below, with what each builds, the platforms its page names and who it fits.
FactoryJet publishes this article and is one of the nine. The order is alphabetical. We read every company's own voice agent page on 29 October 2026 and describe only what it says. We have not hired the other eight or tested them on the same calls. If you want a ready-made AI receptionist or a platform to build on yourself, our list of AI receptionists and voice agent platforms covers those with their published prices.
Nine voice AI companies that build custom agents
Many voice AI companies sell a platform. The nine below are AI voice agent development companies. A firm that sells AI voice agent development services builds the agent for you and connects it to your phone system, CRM and booking tools. You hire it for a project. Each entry links to the company's own voice agent page.
Appinventiv
What it builds: Eight listed voice services, from voice strategy and voice interface design to custom agent builds, multilingual adaptation, model training and monitoring.
Platforms its page names: Whisper, Kaldi and Coqui TTS for speech, LangChain and Rasa for dialogue, telephony over SIP (the standard that carries internet phone calls) and WebRTC. No Vapi or Retell named.
Who it fits: Enterprises that want strategy, build and support from one large firm.
Appinventiv lists nine industries for voice work, including healthcare, fintech, lending, automotive, travel and restaurants, and says it serves conglomerates, enterprises and startups. Its stack leans on open source speech models, which matters if you want to avoid paying a platform by the minute later.
Read Appinventiv's voice agent pageAppther
What it builds: Inbound and outbound agents, IVR replacement (IVR is the press-a-number phone menu), appointment booking, CRM integration, multilingual voice, evaluation and guardrails, and tuning after launch.
Platforms its page names: Twilio for telephony, ElevenLabs for speech, OpenAI, Claude and Gemini as models, LangChain, on Python and AWS. The page says the stack is chosen per deployment.
Who it fits: Teams that want an engineering shop to pick the stack call by call.
Appther is one of the few build firms that prints its stack on the service page. It also lists IVR replacement as its own service, which is the job most call centers start with: the press-1-for-billing menu is the first thing a voice agent can take over.
Read Appther's voice agent pageConcret.io
What it builds: Inbound, outbound, booking and lead qualification agents, enterprise builds and white-label builds for agencies.
Platforms its page names: Salesforce, HubSpot and Workato as partner platforms; ServiceNow, Oracle, SAP and AWS as integration targets. The page says its agents are built from the ground up and names no voice platform.
Who it fits: Salesforce and HubSpot shops that need the call to land as a CRM record.
Concret.io names three buyer groups: enterprise and mid-market, agencies and SaaS companies, and smaller growing businesses. Its CRM partner list is the reason to call it. If your sales team lives in Salesforce, ask to see a call turn into a lead record with the transcript attached.
Read Concret.io's voice agent pageFactoryJet
What it builds: Custom AI voice agents and AI receptionists, built inside the phone system and CRM a business already runs, then supported after launch.
Platforms its page names: None named here. The agent connects to your phone carrier and works beside the contact center platform you already run, through their APIs.
Who it fits: A call center, restaurant group, dealership or office whose calls depend on its own systems.
FactoryJet publishes this list and is on it. We design, build, implement and support the agent, and the client owns the code. The agent answers, qualifies, books, writes the call summary into the CRM and passes the caller to a person with the notes attached. We show working software on your own data before a contract. The build is a fixed price per phase, quoted in writing; changes are quoted and approved per request; there is no monthly minimum.
Read FactoryJet's voice agent pageGroovy Web
What it builds: Inbound calls answered with CRM context, booking and rescheduling, outbound reminders and surveys, lead qualification and hand-off to a person with the transcript.
Platforms its page names: Twilio, Vonage and RingCentral for calls, ElevenLabs and PlayHT for voices.
Who it fits: Startups and product teams adding a voice agent to their own product.
Groovy Web says it serves startups and product teams. It also publishes one of the three build cost guides used in the cost section below, and in that guide it calls Retell and Vapi platforms you rent and not own. Ask which side of that line your quote sits on.
Read Groovy Web's voice agent pageIntellectyx
What it builds: Voice agents for customer service, sales calls, lead qualification and voice surveys, with CRM, ERP, helpdesk and IVR integration.
Platforms its page names: None named. The page describes speech recognition, VoIP and SIP gateways and its own pre-built agent frameworks.
Who it fits: Larger companies in retail, healthcare, contact centers and banking.
Intellectyx lists four voice industries: retail and ecommerce, healthcare, contact centers, and banking and finance. It says it uses pre-built agent frameworks of its own. Ask what you own at the end if the agent sits on that framework.
Read Intellectyx's voice agent pageMaster of Code Global
What it builds: Voice bots for client support, lead qualification, recruitment screening, appointment booking and debt recovery, plus case studies in banking, automotive and real estate.
Platforms its page names: OpenAI, Google Dialogflow, Amazon Lex, Twilio and Azure Speech; Salesforce, HubSpot, SAP and Zendesk; contact center suites Genesys, NICE and Avaya.
Who it fits: Mid-market and large contact centers already on Genesys, NICE or Avaya.
Master of Code Global names the most contact center suites of any firm here, and its page cites work for call centers with over twenty thousand agents. It also publishes a voice cost guide we quote below. Debt recovery is on its list, which puts outbound calling rules at the top of the scope.
Read Master of Code Global's voice agent pageRaftLabs
What it builds: Inbound answering and routing with a briefing for the person who takes over, booking within approved rules, lead qualification that records consent, research interviews and opted-in outbound follow-up.
Platforms its page names: None named. The page says SIP or programmable telephony, and lists its own voice products Voixbery, Perceptional and Call Eva.
Who it fits: A team that wants to prove one call type before buying more.
RaftLabs tells buyers to start with one repeated call type and a clear result, and offers a first paid phase that is a call flow audit, a phone proof or one bounded workflow. Its qualification agent records consent and the caller’s own words, which is the right default for outbound work.
Read RaftLabs's voice agent pageSoftcery
What it builds: Fixes and rebuilds of existing voice agents for B2B software companies: latency, naturalness, reliability, platform migration, self-hosting and model tuning.
Platforms its page names: Names Retell, Vapi and Bland as managed platforms it moves clients off, toward agents the client owns.
Who it fits: A software company whose voice agent already works but is slow or clunky.
Softcery’s home page headline is about fixing a clunky voice agent, and it sells agents the client owns outright. It suits a team that built on a platform, proved demand and now wants control. Its demos include a legal receptionist and a hotel receptionist.
Read Softcery's voice agent page
Comparison table: voice agent builders side by side
What each firm's own page said on 29 October 2026
Swipe sideways to see every column.
| Company | Tools named | Who it fits |
|---|---|---|
| Appinventiv | Whisper, Kaldi, Coqui TTS, LangChain, Rasa | Enterprises that want strategy, build and support from one large firm |
| Appther | Twilio, ElevenLabs, OpenAI, Claude, Gemini | Teams that want an engineering shop to pick the stack call by call |
| Concret.io | No voice platform named; Salesforce, HubSpot, Workato | Salesforce and HubSpot shops that need the call to land as a CRM record |
| FactoryJet | Chosen per project; works beside your current contact center platform | A call center, restaurant group, dealership or office whose calls depend on its own systems |
| Groovy Web | Twilio, Vonage, RingCentral, ElevenLabs, PlayHT | Startups and product teams adding a voice agent to their own product |
| Intellectyx | None named | Larger companies in retail, healthcare, contact centers and banking |
| Master of Code Global | OpenAI, Dialogflow, Amazon Lex, Twilio, Genesys, NICE, Avaya | Mid-market and large contact centers already on Genesys, NICE or Avaya |
| RaftLabs | None named; own products Voixbery, Perceptional, Call Eva | A team that wants to prove one call type before buying more |
| Softcery | Moves clients off Retell, Vapi, Bland | A software company whose voice agent already works but is slow or clunky |
Two patterns stand out. Only Softcery and Groovy Web mention Retell or Vapi at all, and both describe them as platforms you pay for by the minute, with a custom build as the route to owning the agent. Three of the nine (Intellectyx, RaftLabs and Concret.io) name no voice platform, so ask them directly what carries the call and what you keep at the end.
Build firm, platform or ready-made product
Three kinds of company use the words "AI voice agent". Pick the kind before you pick the company.
- Ready-made AI receptionist. You sign up, load your hours and FAQs, and forward your number. Fastest route for a small office with standard calls.
- Developer platform (Retell AI, Vapi, Bland AI, Synthflow). Your own developer builds AI phone agents on the platform and connects a phone number. You pay the platform for every minute. Speech companies such as Deepgram also sell a Voice Agent API that handles listening, the model call and the spoken reply in one connection.
- Development firm (the nine above). The firm designs the calls and builds the agent. It connects the agent to your phone system and CRM and supports it after launch, and you own what is built.
Paying for voice AI agent development from a build firm is the right call when the call depends on your own systems: a quote that needs your pricing rules, a booking that needs your dispatch board, a call center queue with a team of people behind it. Our guide to choosing between an AI voice agent and a human answering service covers the step before this one.
Send us your five most common call reasons
Tell us your phone system, your CRM and the calls your team gets most. We will tell you which ones a voice agent can take, whether the agent built into your phone platform would do the job, and what a custom build would need. Bhavesh, the founder, usually replies within 2 to 3 hours.
Get a call flow reviewHow to evaluate a voice agent builder
Give every firm the same five tests. Their answers will separate a demo from an agent you can put on a live line.
- Test latency on your own call recordings. Pull 20 real calls from your phone system, with names removed. Ask each builder to play them through its agent and time the gap between the caller finishing a sentence and the agent starting to speak. A demo script written by the vendor hides the slow cases: accents, background noise, a caller who talks over the agent.
- Hear the hand-off to a person. Ask for a recording of a transfer. The person who picks up should get the caller’s name, the reason for the call and what the agent already did, before they say hello. A cold transfer that makes the caller repeat everything is worse than no agent.
- Settle call recording consent and AI disclosure. Some US states require every party on a call to agree to recording. For outbound calls, the FCC treats an AI voice as an artificial voice under the TCPA (details below). Ask where the agent says it is an AI, where it asks for consent, and where that consent is stored.
- Watch the CRM write-back. The call is only useful if it lands in your system. Ask to see a call create or update the right record in your CRM, booking tool or help desk, with the summary, the outcome and a link to the recording. Then ask what happens when the CRM is down for ten minutes.
- Ask who owns it and who supports it. Get in writing which repository, prompts, phone numbers and accounts you receive at handover, and who fixes the agent when a carrier, a model or your CRM changes. An agent that nobody watches gets worse quietly.
For the wider vetting list, send each firm the 15 questions to ask an AI development company.
What a custom AI voice agent costs to build
These are build ranges published by three firms that sell this work. They are in US dollars, they cover the build only, and none of them is a FactoryJet price. We re-read each source on 29 October 2026.
Swipe sideways to see every column.
| Source | Published build ranges |
|---|---|
| Groovy Web (6 Jul 2026) | Single-purpose agent for a small business: $3,000 to $12,000. Multi-intent agent: $12,000 to $30,000. Enterprise: $20,000 to $120,000. |
| Master of Code Global (updated 14 Sep 2026) | MVP (a first working version): $10,000 to $25,000. Mid-tier with CRM integration: $25,000 to $50,000. Advanced (multilingual, compliance): $50,000 to $150,000+. Enterprise-grade: $150,000 to $300,000+. |
| Softcery (3 Jul 2026, its own estimate bands) | Configured platform agent: $1,000 to $15,000. Custom integrated build: $80,000 to $200,000. Compliance-grade system: $180,000+. |
The spread is wide because the scope is. One call type on one phone line sits at the bottom. Several languages, deep CRM and ERP connections and regulated data push a build to the top. FactoryJet quotes a fixed price per phase in writing after a short scoping call. Changes are quoted and approved per request, and there is no monthly minimum.
The FCC rule every outbound voice agent must follow
On 8 February 2024 the Federal Communications Commission adopted a Declaratory Ruling that calls made with AI-generated voices are "artificial" under the Telephone Consumer Protection Act. In plain words: an AI voice calling a consumer is held to the same rules as a prerecorded robocall, including prior express written consent before a telemarketing call. Read the FCC news release on AI-generated voices.
Inbound calls, where the customer rings you, are a different case, but recording consent still applies, and some US states require every party to agree. Outside the US, check local rules on recording and marketing calls. Ask every builder to show where the agent discloses that it is an AI, where it records consent and how it handles "stop calling me". This is not legal advice; check your use with counsel.
Voice agents FactoryJet builds by industry
- AI call center agents: agents that work beside your existing contact center platform and pass calls to your team with notes attached.
- Restaurant AI voice agents: orders, bookings and catering inquiries for restaurant groups.
- Automotive AI voice agents: service booking and parts orders for dealerships.
- AI receptionist: answering, qualifying and booking for offices and field service firms.
Other voice AI companies you will meet in search
We pulled the live Google results for "ai voice agent development company" in the US and the UK on 29 October 2026. Here is who you will meet if you keep searching, and what each kind of page is for.
- Platform vendors writing lists. Retell AI ranked with its own list of enterprise voice agent vendors, and Rasa and Vellum with platform guides. Useful for platforms; each one sells a platform.
- Development firms writing lists. RaftLabs and Intellectyx each publish their own list of voice agent development companies, and Azilen ranked in both the US and UK results with a list of agent developers. Every vendor list, this one included, is written by someone who sells the service.
- Reddit threads. Reddit held two of the US top ten and the top UK result, mostly builders comparing platforms. Good for honest notes on latency and failure cases.
- Carriers. Vonage ranked in both markets with its own voice agent API. It sells the voice API that builders use.
For AI agents beyond the phone, read our comparison of AI agent development companies.
See a voice agent working on your own calls
Send a few call recordings with names removed, or your top call reasons. We build a working demo on your data before you sign anything, then quote a fixed price in writing. You own the code.
See a demo on my dataFrequently Asked Questions
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Bhavesh Barot
Founder & CEO
Founder & CEO of FactoryJet, which he started as a B2B ecommerce marketplace. FactoryJet has served 500+ businesses and builds online stores, B2B portals, AI agents and AI search.
Related reading
- 10 AI Agent Development Companies Compared (2026)Ten AI agent development companies compared by what each one publishes, with a link to every offer, 2026 market cost ranges from named sources and one question to ask each firm.
- Best AI Agent Development Companies for Manufacturers (2026): 14 AI Manufacturing Companies ComparedA fact-checked guide to the companies that build AI for manufacturers and distributors in 2026, grouped by what you are buying: plant-floor and industrial-data AI, ready-made quote and order software, or a custom agent on your ERP. What each sells, which systems it names, who it suits and one question to ask it. FactoryJet is on the list and says so.
- Best AI Agent Development Companies and AI Automation Agencies in the UK (2026): 15 ComparedA fact-checked guide to UK firms that build AI agents and AI automation for small and mid-size businesses, in London and the regions. Where each one is based, who it suits, which systems it works with, what it publishes about price, and how to choose. FactoryJet is on the list and says so.
