Around the World
Phone for use in US and Japan
1) Japan does not offer prepaid sim cards.
2) You have to have a 3G phone in Japan.
3) Their 3G frequencies run on WCDMA 1900 and 2100 frequencies.
It would appear that any recent AT&T 3G phone with the 1900 frequency band would work in Japan however you would need to verify that with AT&T as well as the data and voice rates you will pay to use your AT&T phone in Japan.
You may wish to inquire whether the new 3G iphone will work in Japan. It could be your phone solution.
Maybe others on this forum that travel to Japan could shed more information for you, but anyway this is what I found about the subject. Hope it helps and enjoy the trip.
Sony Ericsson Z750a
Samsung Blackjack II
AT&T (HTC) Tilt
The SoftBank shop at Narita does sell Sim cards for use in japan but it has to be returned before you leave.
http://buynow.theunet.com/T3-Quad-band-FM-Dual-Sim-S ... »
I've bought one already like this.