WhatsApp Chatbot with OpenAI Integration

WhatsApp + OpenAI Assistant Integration
Project Overview
I need a developer to set up and configure a WhatsApp Business integration using Twilio, directly connected to my OpenAI Assistant.
The goal is to have a fully functional WhatsApp chatbot where every incoming WhatsApp message is sent to my defined OpenAI Assistant, and its response is returned back to the user without any extra system prompt or modifications.
This setup is only for a testing phase, but it must be stable, functional, and production-ready if needed later.
Scope of Work
1. Twilio Setup
Create and configure a Twilio account (email will be provided).
Verify account and select a U.S. number (preferably Miami, Florida) enabled for WhatsApp.
2. WhatsApp Business Integration
Configure Twilio Sandbox/Business number for WhatsApp.
Ensure two-way messaging is active.
3. OpenAI Assistant Connection
Connect Twilio directly to my OpenAI Assistant using the assistant_id:
Use the provided OpenAI API key for authentication.
No external or custom base/system prompts should be used.
4. Webhook / Backend
Implement webhook or backend script to handle:
Incoming WhatsApp messages → Forward to OpenAI Assistant
Responses from OpenAI → Send back via Twilio WhatsApp
Host the webhook on a reliable service (e.g., Render, Vercel, Replit, or other).
5. Testing & Delivery
Test full flow with real WhatsApp users.
Share clear documentation/instructions for future updates.
Handover with credentials and tested setup.

Timeline
Delivery: Within 2 days (max)

Deliverables
Verified Twilio account with working WhatsApp U.S. number (Miami preferred).
Connected and tested integration with my OpenAI Assistant (no prompt overrides).
Working end-to-end WhatsApp AI chatbot ready for testing.
Documentation of setup and usage instructions.