I've read myself silly trying to understand this, so I'm really hoping someone can help clear this up for me. I'm looking for an iPhone to use on T-Mobile, so unlocked. I was told by someone to look for an iPhone that is 3.1.2 or earlier firmware. Then, I've been told by someone else I need to look at the modem firmware and make sure it is not 05.12.01. So if someone has a 3GS that is 3.1.2 but 05.12.01 does that mean it cannot be unlocked? How would a phone get the updated modem firmware 05.12.01 but still be on 3.1.2? Thanks for your help.