Okay, so I managed to BT Broadband Talk working as my VoIP provider in 3cx, briefly, and it does connect, and when it connects, it does work, but then I get this a few seconds later... 01:50:08.621 ClientRegs:nFailure [CM504007]: Next attempt to register 10000@BBT is scheduled in 5 minute 01:50:08.621 ClientRegs:nFailure [CM504005]: Registration failed for: 10000@BBT; Cause: 400 Too many contacts; from IP:188.8.131.52:5060 01:49:33.390 ClientRegs:nSuccess [CM504004]: Registration succeeded for: 10000@BBT 01:49:33.172 ClientRegs::Register [CM504003]: Sent registration request for 10000@BBT then the same thing happens all over again. I've tried to search for what "Too many contacts" actually means, but it seems any info on SIP errors or how to resolve them is hard to find, even on the Google! Ben Edit: Does "Too many contacts" mean that 3cx is trying to send contact addresses to the VoIP provider but it isn't accepting them? If so, how do I get 3cx to not send them. It's causing the line to unregister.