I have an Iphone 4 with iOS 5.1.1 and baseband 4.12.01. The phone is locked with at&t and I don't have the at&t sim. I hactivated the phone, did a jailbreak and tried unlocking with Ultrasn0w and SAM, but to no avail. I preserved the SHSH using TinyUmberalla before jailbreaking though. I used redsn0w to jailbreak the phone.
I desperately need to unlock this phone, whether by downgrading the baseband (I dont know how, somebody please help), or otherwise. Else its just a piece of trash for me. Please people, help me out!
Thanks so much!