Hi Experts I have iPhone 3GS with iPad baseband 06.15.00. The phone was upgraded to the above baseband to unlock it using ultrasn0w on iOS 4.x. The phone is unlocked but I would like to upgrade to iOS 5.1 Recently found that AT&T will unlock old iPhone if you finished your contract. If I am to upgrade to iOS 5.1 will it upgrade the baseband and will it work. Please advise?