Unlocking ATT Iphone 4

[Grimreaper]

My friend sold me his iphone 4, after his contract was over, (att), And now I want to unlock it. I know there are several threads and articles about this but there is one thing I don't get.
I read this article, about a guy who wanted to unlock his iphone, and contacted att, backed up and restored it in itunes, but it didn't work, then the att rep told him he needed an active sim card in the phone in order to work. Is that for everybody?
And what does it mean to have a "active" sim card. Wouldn't active mean that its still connected to the network or somthing? But If you are off contract and no longer using it as a phone is it even possible for a sim card to be "active" when you put it in? I have a sim card or 2 in old phones, Could I just pop those in? They aren't att though, So I'm not sure.

Can you help me out?

 

[Gregoris]

My friend sold me his iphone 4, after his contract was over, (att), And now I want to unlock it. I know there are several threads and articles about this but there is one thing I don't get.
I read this article, about a guy who wanted to unlock his iphone, and contacted att, backed up and restored it in itunes, but it didn't work, then the att rep told him he needed an active sim card in the phone in order to work. Is that for everybody?
And what does it mean to have a "active" sim card. Wouldn't active mean that its still connected to the network or somthing? But If you are off contract and no longer using it as a phone is it even possible for a sim card to be "active" when you put it in? I have a sim card or 2 in old phones, Could I just pop those in? They aren't att though, So I'm not sure.

Can you help me out?

Well an active sim means you need to have a ATT sim card thats still active and being used so if your friend has one thats out of contract then ATT will unlock it for him if you can get your friend to go to ATT and request an unlock for the device or unless you have your own working ATT sim they might unlock it for you