This is probably one of those things where if I have to ask, it means no. I simply have a 3GS that fulfilled its contract with ATT. I'm selling it on ebay, but I don't want to mislead buyers by saying it's unlocked if it's not. It's been upgraded to iOS 5, and modem firmware is 05.16.05 I'm not even sure what unlocked means. I mean, can't a 3GS just accept any SIM card and work on a GSM network worldwide? I don't need an in depth explanation, I just want to correctly advertise and sell my phone.