Hi there, I was already writing about this problem, and I still didn't managed to fix it. I thought it was a NAT problem, but now without NAT the problem still remains. The error is like this, when I call from pstn, the call goes trough Cisco AS5300, then goes to FS, then to it's final destination - Ip Phone. Now you can answer the phone, but you can't hear anything on any side. And FS returns lots of SIP 415 (unsupported media type) to Cisco AS5300. When you call from Voip phone to the same pstn number it all works well, so I'm starting to be confused more and more. (and in this case there is no 415 messages). I believe cisco is sending something that FS can't understand, in the INVITE's but that's just a wild guess cause I ain't sure what can FS exactly understand very well. Whoever want's I can send him a tcpdump, it's about 7mb tarred, so I can't send it to the list. Thank you all, Josip