Can I trade my iPhone at GameStop for another iPhone?

I have a perfectly good condition iPhone 4. The bad thing is that it is Verizon and I was wondering if I can trade this Verizon iPhone 4 16g black for an AT&T iPhone 4 16g black.

So much as it meets their trade in conditions, which include workability and ESN status, it should not be a problem, however as a GSM iPhone 4 is a little more valuable than a CDMA iPhone 4, be prepared to have to pay to trade.