In March, my iPhone 4 died recently and my provider sent me a new iPhone. My previous iPhone was jailbroken and unlocked because I had one of the unlockable modem firmware versions. However, my new iPhone is on 03.10.01 and this is not unlockable so I didn't even try. I live in Canada and AT&T is not my home network. Recently, I went to the US. When I was there, I though I would try my AT&T GoPhone sim card. To my surprise, it worked! I'm currently on 4.2.1 and firmware 03.10.01. I'm wondering if I update the software, could my phone be relocked?