iOS Developer Needed for VoIP Call Issue Fix (pjsip Integration)

I have a small issue to address. My app is a VoIP iOS application that uses PJSIP to make SIP calls.
However, after some updates were made, outgoing calls are working fine, but incoming calls are not functioning properly.
When I accept an incoming call, there is no audio.

Requirements:
Strong experience in iOS development (Swift/Objective-C).
Familiarity with pjsip or similar VoIP libraries (SIP, RTP, etc.).
Experience with push notifications (PushKit) for VoIP calls.
Ability to troubleshoot issues related to audio streams, network switching, and SIP protocols.
Experience working with background tasks for VoIP apps.

Skills:
iOS Development (Swift/Objective-C)
VoIP Development (pjsip, SIP)
Networking (NAT traversal, network switching)
PushKit (for VoIP push notifications)
Audio Stream Management (RTP, microphone/speaker handling)

Additional Info:
You will be working on a pre-existing iOS app that uses the pjsip library for making VoIP calls.
Please only apply if you have proven experience with VoIP-related issues, especially around network changes during calls.