Sorry my thoughts weren't correct. When disabling rtpproxy in the local kamailio installation, I have one way audio. The caller, local SIP user, can hear audio from the user registered on the PSTN address, which also can't hang up the call.

It seems to me that the kamailio PSTN gateway can't engage rtpproxy correctly when receving a call from the local kamailio+rtpproxy.

I changed the configuration from a the basic one to this here http://kb.asipto.com/kamailio:skype-like-service-in-less-than-one-hour

(I have only updated the outdated functions) and it works well for calls between mobile phones) but again the same problem described above.

If anyone could give me an advice it would be much appreciated

Thanks