Broadband phone problems

[#1]

Does anyone else find their broadband phone cutting out part way through calls?  I use the Speedtouch 316 router and have plugged a normal cordless phone into its phone port.  I did have it working OK (apart from calls regularly cutting out after only 1 minute) but I had to reset my router and now all I get is a continuous unavailable tone.  I've entered the server and proxy details and all the right port numbers, can anyone suggest what might be wrong? 
Andrea
http://www.allaboutoffice.co.uk

[#2]

Have you tried using a software phone to see if the same issue is apparent on there?

[#3]

I don't sit near my PC at the times when someone might ring me.  My mum rang me today and we were only able to speak for about a minute before it cut out, that was using a plain BT wired phone plugged into the Speedtouch router.
I have bought a differet ATA VOIP router box as well but I haven't been able to get it to work, it asks for things like service name and I can't suss out whether I've got the right settings.
Andrea Jones

[#4]

Hi there,
You can find some setup info here.
If it's the Speedtouch 716 you have with an ATA, you can find the setup guide specific to that here.