i recently bought an iphone and unlocked the basic functions (ipod, safari, etc) but was unable to unlock the phone function. ive decided to sign up with ATT. Can i go into the store, sign up for a contract with a dataplan, bring home the phone ATT gave me, take out the sim card and pop the sim card into my iphone? will this work? i heard to get the data plan for iphone, i have to sign up through i tunes. If so, do i need to re-lock my iphone?