AI Voice Agent Developer

I'm looking for an AI Voice Agent Developer to build an initial working demo for a business I'm developing. The goal is to create a reusable AI phone receptionist that can later be customized for businesses in different industries. For this initial project, I need a working demo that can: * Answer inbound phone calls naturally * Answer basic business FAQs * Collect caller information and qualify leads * Check appointment availability * Offer available appointment times * Book an appointment * Transfer the caller to a human when necessary * Send a confirmation SMS if feasible * Handle errors correctly without telling customers something was booked when it wasn't Preferred experience: * Vapi and/or Retell AI * OpenAI * Twilio * API and webhook integrations * n8n / Make * Python/FastAPI or Node.js * Google Calendar or similar scheduling integrations * CRM integrations * Supabase/PostgreSQL is a plus IMPORTANT: I'm not looking for someone who only knows how to create prompts or configure a basic Vapi assistant. I need someone who understands the backend/API side and can make the voice agent perform real actions. This first $200 project is intended as a proof-of-concept and developer trial. If the project goes well, I'm looking for someone I can work with long-term as I acquire clients who need customized voice agents and integrations. I want the system designed so components can be reused for future clients rather than rebuilt from scratch each time. All code, workflows, and configurations created for the project must be delivered to accounts/repositories that I control. When applying, please include: 1. Your experience with Vapi and/or Retell AI. 2. An example of a voice agent you've personally built. 3. Any API, CRM, calendar, or scheduling integrations you've built for voice agents. 4. A demo recording or test phone number if you have one. 5. What backend technology you recommend and why. 6. Whether you can complete the initial demo within approximately 2–4 days. 7. Whether you're interested in ongoing paid work as new clients are acquired. Budget: $200 fixed price for the initial demo/test project.