How to wipe an IPhone of its carrier?

Ok, heres the deal. And if it helps, I live in the USA and so does my friend.

My friend was living overseas in Japan for awhile, and bought an Iphone there. Now hes home, and he bought a new phone. He gave me this Iphone because I figured I could use it as an ipod, but the japanese carrier is still on it and won't let me access the phone.

How do I wipe this japenese carrier off this Iphone? I have read that you can use an active sim card to use your iphone as an ipod, but it has to be the same carrier as the iphone has. And, ofcorse, no one here has a japanese carrier.

I just need a clean quick way to clear all carrier data from this iphone.

At the side

Which iphone is it? Just eject the sim if it has one, and put a prepaid sim in there (I would recommend att)

They do this kind of thing every other day. Just bring your special i-phone in to see the special people that represent your phone carrier. Call ahead and try to set up an appointment to get your phone reset for American service. They will get you for a new SIM card and a little extra for the special service. Some places are set up for this and some are not. So, like I said call ahead and see where you need to go with it.

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