I just picked up a used Mytouch 3G to mess around with until all the new Androids start hitting the market this summer (been an iPhone user till now). Anyway I want to UNLOCK it to use it on AT&T (yea, I know, no 3G but for $120 I don't care - I can always resell it). My question is: This phone didn't come with a SIM card. Do I need a T-Mobile SIM (active or inactive) to unlock it or can it be done with no SIM or my AT&T SIM? If it needs a T-Mo SIM (and I'm not a T-MO subscriber) what can I do? Would a Pre-paid SIM work? I can always get one off eBay for a couple bucks I guess.