I have a VOIP system with a hardwire connect and everything works just fine.

When I use my Android phone to connect to T-Mobile for VOIP service, NAT kills off the audio component of the phone call. The connection is built properly, but the RTP analog data packets are clearly being dropped. Is there any solution to this issue?

I tried disabling SIP-ALG, but that breaks the hardwire VOIP system.

Thanks!