Twilio / Retell Number & SIP Setup

I’m building an AI phone-answering SaaS for Australian businesses. The stack is already in place—Manas AI drives the conversation logic, Retell generates the voice, and Twilio supplies the numbers. Where I’m stuck is getting Twilio to cooperate: acquiring and configuring the phone number correctly and wiring it into a fully functional SIP trunk so calls flow cleanly to and from the AI layer.

There are no explicit error messages yet; the call simply never reaches the Manas/Retell pipeline, so I suspect something is mis-set in Twilio’s multi-layer configuration. If you’ve previously stood up Twilio numbers alongside SIP trunking for voice AI or contact-centre solutions, you’ll feel right at home.

What I need from you
• End-to-end configuration of a Twilio Australian phone number, confirmed operational for inbound and outbound calls.
• Creation (or correction) of the SIP trunk with appropriate authentication, routing and codec settings so audio hits Retell without distortion or lag.
• Quick walkthrough or concise doc explaining what you changed so I can replicate it for future clients.

When you apply, focus on your relevant Twilio/SIP experience—brief war stories are more valuable to me than a long proposal. Once the number rings through the AI pipeline reliably, we’re done.