Help with a Nokia 3595 for use with TMobile Prepaid Sim

I have an unlocked Nokia 3595 that I'd like to begin using on the T-Mobile network. I purchased a T-Mobile prepaid sim card and put it in the phone...but it never shows that I have service[i.e. I can't make any calls]. Even in places where I have previously gotten reception with this phone when it was using AT&T it still shows no service[even in places that people I know with T-Mobile get perfect service!]. Any help or advice anyone can give me would be GREATLY appreciated! Thanks!

im not sure if network is the problem of your phone but were not losing anything if we try. sellect menu, select setting, sellect network services, sellect system selection,sellect automatic. hope it works.

It's still not working but i GREATLY appreciate you trying to help! I may end up giving up and going back to AT&T.