Help Help! No signal after 2.1 update!!

Today i got my phone completely wiped and the 2.1 firmware put on it at carphone warhouse, this was because the phone managed to lock its self with the pattern unlock in my pocket and the device wouldnt accept my gmail... anyway, after getting the new update i lost signal the areas that i normally get full signal, in my bedroom i used to have full bars, now nothing. however can sometimes et to full bars when i go out side or travelling, but most of the time there is nothing. this is soooo annoying as i cant send or recieve texts/calls.
is there something i am ment to have done or can do to get signal back?
is the phone broken?
is it a problem with t-mobile?
or have carphone warehouse broke it when they did the update?

please please can anyone help me:(