I recently acquired two Fritz!Box Fon's from trademe. I've received the first one, and it's running great except for one issue.

I'm using it as an ATA only, as the ADSL modem seems to be a German Annex B model and I'm not sure I'm willing to risk the Annex A firmware conversion. I have it connected to my network, the PSTN phone line and two phones, all of which is working smoothly (after some trial and error, and using this cable: http://www.geekzone.co.nz/inquisitor/3874, the instructions for which I am extremely grateful for).

The issue I have is that whenever I make a call from another phone on the same PSTN line (but not an extension of the Fritz!Box Fon) the extensions of the Fritz!Box Fon ring. I can disable that by preventing them from responding to the fixed line at all, but in that case they don't respond to incoming calls either. All calls made from other phones on the same line are logged as "incoming calls" on the Fritz!Box.


My second question is about German VoIP providers, in case anyone is familiar with them. We will mostly be using this setup to communicate with a person in Dortmund, Germany. She currently does not have an internet connection. I've heard that sipgate.de offers free DID's in Germany, however I'm having difficulty navigating their website. Can anyone confirm whether they do offer free DID's in Dortmund, and also whether local calls within Germany are free or not?