Can I unlock my iPhone 4 without internet?

I used my iPhone 4 under an AT&T contract but I recently terminated it so the phone's just been sitting around for about a month. My friend told me he wanted to buy it, but he wants to use it for T-Mobile. Since the phone isn't currently under any contract, it can't be connected to the internet (unless you can connect to Wi-Fi but I'm not sure if you can) so I wanted to know if it was still possible to unlock it so it could be used for T-Mobile. And if so, should my friend try to unlock it himself or take it into a shop to get it unlocked?

You need call att to unlock it.

You can complete the entire unlock request process online with AT&T.
You can found details answer from this link
http://unlockanyattiphone.com/