Hi all I do have a problem with getting a propper interconnection to our new carrier.. Situation as following User àClass5 switch àKamailio àcarrier I always get the ip of the class5 switch in the contact. But my carrier needs the kamailios contact ip – because of the ack handling. I replaced in the pstn routing parte the contact by remove_hf("Contact"); append_hf("Contact: <sip:xyz@a.b.c.d>\r\n"); This worked – but the bye did not work any more. Please help me on that topic … I am searching for a solution for more than 8 weeks now …