Hello, I currently have a jailbroken (with jailbreakme.com and unlocked with ultransn0w 1.2) iPhone 3G on bb 6.15.00. I was wondering if it is possible to upgrade to 4.2.1 without changing the baseband or losing my unlock, as I am a T-Mobile user. The iPhone works fine as is, but I can't download many App Store apps running anything lower than iOS 4. It is also my understanding that the baseband I am on is required for T-Mobile. I DO NOT want to lose my unlock as I had spent three days jailbreaking and unlocking the darned thing. Thanks!