Sorry, but his also has nothing to do with AT&T nor with Apple. The reseller from whom you purchased your iPhone does not sell unlocked iPhones; only Apple's own stores offer unlocked iPhones in the US. I can't even determine that First Class is authorized to sell the iPhone at all, though they may be and I just can't find the information.
If you were told by First Class Wireless that they were selling you unlocked iPhones, then they were either completley misinformed or just flat lied to you. Neither AT&T nor Apple has any responsiblity in this matter. Your issue and recourse is with First Class Wireless and you will need to work this problem out with them.
Note that the Gevey SIM is illegal in almost every country in the world, so if you purchased the Gevey SIM also from First Class, they are an extremely unethical business and are quite possibly engaged in criminal activity, though I am not certain whether it is illegal to sell the Gevey SIM or just illegal to use one.