AI Voice Agent Developer (Vapi / Twilio / GoHighLevel), Inbound and Outbound Builds

We are an AI automation agency. We build 24/7 AI voice agents for local service businesses, clinics, and e-commerce brands. Our agents answer inbound calls in a natural, human-sounding voice, greet callers, answer FAQs, qualify leads, book appointments into the client's calendar, route urgent calls, and log a summary after every call. They also make outbound follow-up and reminder calls. We are looking for a developer to build and ship these systems as part of our delivery team. You do the technical build. We handle sales, client requirements, and handoff. **Two rules to read before applying** 1. Do not need to build a voice model from scratch. We do not want a custom speech engine. You build on existing platforms (Vapi as our primary, with Retell or the OpenAI Realtime API where they fit), using Twilio for telephony and ElevenLabs for voice. This keeps builds fast to ship and easy to maintain. 2. Do not need to build on your personal accounts. Every live client build runs on the client's own platform accounts (their phone number, their Vapi and Twilio, their CRM), set up in their name with us holding admin access during the project. Internal demos run on our accounts. You never host a client's live system on a personal login. On completion you hand over full access and documentation so any team member can maintain it. Note: these are third-party platforms we configure, not software we own. Your job will be to assemble and integrate them. Scope of work: Voice agent setup. Build inbound and outbound agents on Vapi (or Retell where it fits), using ElevenLabs for voice and low-latency speech-to-text (Deepgram or Whisper). Includes a custom greeting and brand voice, FAQ answering, qualification questions, and appointment-booking logic. Telephony. Connect Twilio or SIP for call routing, inbound handling, missed-call callbacks, after-hours coverage, and multi-line setups. Appointment booking. Real-time booking and availability sync through Calendly or Google Calendar, with confirmations. CRM and automation. Push call logs, transcripts, and lead data into GoHighLevel, HubSpot, or Zoho using webhooks, Make.com, N8N, or Zapier. Add and tag contacts, update pipelines, and trigger workflows. Post-call actions. Send SMS or email follow-ups based on the call outcome, deliver voicemail-to-text to email, and log searchable transcripts with daily or weekly call summaries. Routing and escalation. Route calls by urgency and transfer to a human on defined trigger phrases, for example a request for a manager, billing or legal disputes, or emergencies. Accuracy and guardrails. We have zero tolerance for hallucinated information. The agent must stay grounded in the client's supplied FAQs, SOPs, pricing sheets, and website content. Build in strict prompt guardrails, grounding, and human-transfer fallbacks so the agent never invents pricing, availability, or policy. Advanced builds. Some projects also need multi-language handling, complex workflow automation (for example, pre-qualify, then book, then send a follow-up), outbound campaign calls, real-time data lookups such as order or inventory status, and integration across multiple systems (CRM, ERP, payments). Our stack Voice: Vapi, Retell, ElevenLabs, Deepgram or Whisper Telephony: Twilio or SIP Automation: Make.com, N8N, Zapier CRM: GoHighLevel, HubSpot, Zoho Booking: Calendly, Google Calendar Build levels and turnaround Builds fall into three levels. Please estimate against them. Basic (inbound and booking): one line, custom greeting, up to 20 FAQs, call routing, voicemail-to-text, booking integration, and call summary reports. Target turnaround 7 to 10 business days. Mid: everything in Basic, plus outbound follow-ups and reminders, lead qualification (hot, warm, cold), CRM and booking integration, up to three lines, and call transcription with searchable logs. Target turnaround 14 to 18 business days. Advanced: multiple lines, multi-language (English plus one), complex workflow automation, outbound campaign calls, real-time data lookups, and multi-system integration. Target turnaround 21 to 28 business days. Our delivery follows five steps: discovery and call-flow mapping, script and voice setup, agent build and integration, testing and revisions, then launch and training, where we deploy to production, share dashboards and logs, and train the client. Required skills Voice AI platform experience (Vapi, Retell, or equivalent) Telephony and SIP routing (Twilio) API integration and automation (webhooks, Make.com, N8N, Zapier) CRM integrations (GoHighLevel, HubSpot, Zoho) Guardrail and grounding design for accuracy-critical agents Clean, documented builds that another developer can pick up and maintain Ownership and handoff (required) You build inside accounts we or the client own, covering Vapi, Twilio, and the CRM. Nothing runs on your personal accounts or tools. On completion you provide full access and documentation so any team member can maintain the system. The live agent must never depend on a login that only you hold. How to apply Send the following: A fixed-price estimate for a standard inbound and booking build Your hourly rate for ongoing maintenance and optimization after launch Examples of how you enforce accuracy and prevent hallucinations