Hey Guys, I bought a phone 4s off craigslist and I thought I was buying an ATT-locked phone. But it turns out that its suppose to have a different model number if it was locked by ATT. So I looked up the iPhone 4S, which was MD234LL (under general settings about), and found out that it is supposed to be factory unlocked? I checked if it was, and it wasn't. The one that apple sells factory unlocked seems to carry the same model #. Anyone have insight about this model number?