I bought an iphone that has 1.1.2 firmware and I already have cingular/AT&T as my carrier. Do I have to unlock the phone to use my cingular sim card in the Iphone? Isn't the unlocking for people that have other networks and want to use the Iphone? Is there a way to just activate it without using Itunes or selecting the option to add the 20 dollar a month extra data plan to your contract?