I have signed up for onenumber which as I understand it allows me to load sipdroid on my android phone and it means that if someone rings my number, both my home phone (Connected via ATA) and my Android Phone will ring. In order to do this I need to change my authorization username to my number and then a -1 so 5559999-1
The problem is that no matter what I try I can't make it work. Won't register/authenticate if I use that Number.
Not all sip clients can handle the -1 try to register it without the -1 and if that works swap with your ATA. I use the 3CX client on my Android and works well, apart from it only seems to work on speaker phone, on my phone.