Why can't i hacktivate my iphone 4s?

I recently bought a iphone 4s from ebay it was already activated or usable then i tryed to update it to ios 6 beta 4 but i didn't pay for the developer thing so i had to restore back to 5.1.1 and all of a sudden i'm stuck at the activation screen and i can't jailbreak or anything can someone help and i don't have a sim card i just bought it didn't plan to activate it

Ios6 updated the baseband, its useless now…
i have a working unlocked 4s for sale or trade… Email me