One way audio after transferring SIP/NAT/Wireless phone


I’m running into a odd problem and hoping that someone can give me some insight. I know it’s a NAT/firewall issue I just don’t seem to know how to solve it.

We have a wireless phone, that works on initial calls. But one you transfer the wireless phone, we no longer receive audio on the wireless phone.

I have all ports forwarded on our wireless router. UDP range 2727-5070 and RTP range of 10000-20000 (set in rtp.conf)

I have nat=yes and canreinvite=yes in sip.conf for this particular phone.

Any help would be greatly appreciated.