Blackjack 2 sim card error - multiple sim cards wont work?

my phone got a sim card error today, and i thought it was just time for a new one. but at the at&t store, the guy tried a new sim card and his own sim card and still didnt work. my friend knee'd me in the leg were my phone was, the phone works fine(music, games, videos, etc). does geek squad or w/e fix these problems? or should i try and get a refurbish blackjack