Hello. I was wondering if you might enlighten me about possibly using my AT&T iPhone4 on a different provider in Japan.

I am moving to Japan in about a week for about 6 months (or possibly more) and want to continue using the iPhone4 that I use in the US with AT&T. I understand that Softbank was the primary provider for the iPhone, but recently, AU is beginning to carry the iPhone as well. I have also found out that Docomo is capable of carrying the iPhone as long as a symbol appears on the phone, but the rates are quite expensive for phones purchased from a provider other than Docomo.

Does anybody have any suggestions? I use a lot of data as well, so I want to know which provider I might use based on best ratea. I have not fidgeted with the iPhone yet, but I understand that if is unlocked and jailbroken, the phone should be capable of connecting to other networks. If this is correct, what is the best way to unlock and jailbreak?

Thank you so much in advance!