Hi Retell Support Team, I'm experiencing one-way audio with my custom telephony integration (Twilio SIP trunk). The user can hear the agent, but the agent cannot hear the user (inbound audio broken). Issue Summary: - Outbound audio works ✅ (Retell → Twilio → User can hear agent) - Inbound audio broken ❌ (User → Twilio → Retell, agent cannot hear user) - Transcript shows only agent responses (no user words) - Twilio detects "Silence Detected: true" What I've Verified: ✅ SIP signaling works (200 OK received) ✅ SDP is correct (valid RTP ports: 59174, 12202) ✅ Codec matched (PCMU/8000) ✅ Configuration verified (Origination URI, Termination URI, credentials all correct) ✅ Tried UDP and TCP transport (no difference) Evidence: - Call SID: CA74deb543b2c2923e824b929db1db9692 - PCAP file shows Retell advertises RTP on port 59174 in SDP - User's voice → Twilio sends RTP to 161.115.177.96:59174 as advertised - But Retell is not receiving/processing these RTP packets Root Cause: The problem appears to be in Retell's infrastructure - RTP packets from Twilio (carrying user's voice) are being sent to the correct IP/port as advertised in SDP, but Retell is not receiving them. This suggests: - Firewall blocking incoming RTP? - Retell not listening on advertised port? - NAT traversal issue? Questions: 1. Why is Retell not receiving RTP packets on the advertised port? 2. Are there any Retell settings I'm missing for custom telephony? 3. Is this a known issue with Twilio SIP trunk integration? I can provide the full PCAP file and detailed logs if needed. This is blocking production deployment. Thanks for your help!