To the best of my knowledge T-mobile phones work with all its mvno's ( Simple Mobile, GoSmart, MetroPCS etc) without even having to unlock them, just needing to put the correct apns for mms/data. Have you tried looking at the Network settings ? I wonder if it could also be a coverage issue since it keeps searching. It could be a couple different possibilities. If you are able to contact from another phone I'm sure they would be willing to try to figure out the problem.