React Native VoIP Server Build

I need a solid back-end that lets a future React Native client place and receive calls with the reliability of a carrier-grade PBX. The server must handle:

• Incoming and outgoing calls
• Call forwarding and call transfer
• Voicemail storage/retrieval
• A flexible auto-attendant (IVR)

My preference is to stay in the React Native ecosystem for the client side, but I’m open to your guidance on the most appropriate SIP/WebRTC stack, media server (Asterisk, FreeSWITCH, Kamailio, etc.), and signalling approach.

Please outline the architecture you propose, the main tech you’d employ, and an estimated timeline for delivering a first working build that can:

1. Register soft-phones via SIP or a comparable protocol
2. Complete internal and external calls with the features above
3. Expose a clean REST/GraphQL API so the React Native app can manage accounts, contacts, and recordings

If you’ve shipped similar VoIP solutions before, a quick note on what you built and the tools you used will help me understand your fit. I’m ready to move ahead as soon as we agree on the plan.