I have a T-Mobile contract and upgraded to the Sony Ericsson K770 last week. Phone worked great for a week but suddenly its stopped working in my house. Basically, the phone is full of bars so you wouldn't expect coverage to be an issue but when I try to receive/send texts or calls I just get a few beeps when I try and dial. Thought it was a network issue but when I put the Sim Card into my old phone (also Sony Ericsson) it works fine. Went to the shop to complain and got a replacement K770 but the same problem happens!
Very strange as I haven't changed network provider, my 5 year old Sony Ericsson works ok but my new Sony Ericsson refuses to connect when in my house.
I'll probably go back to the shop tomorrow and try and swap to a Nokia but can anyone offer any advice as to what could be the problem as I quite like the phone (apart from it not working

)
Cheers