Good Question
I have also wondered the same thing regarding carrier policies in other countries (especially when using packets over the 3G network). In Japan, Softbank and Docomo both use 3G networks (for 3G iPhones). Either of these carriers should work with your unlocked 3G.
I do not know the answer to your question specifically, since I could not find anything on their policies regarding "third party" handsets; but here is the link to Softbank's and Docomo's English customer service pages:
http://mb.softbank.jp/mb/en/support/
http://www.nttdocomo.co.jp/english/support/inquiry/
The quickest way to get to the bottom of this is to contact them directly with your question. Trying to interpret policies on your own (that sometimes seem to change depending on who you are talking with) is usually a painful experience in Japan.
Good luck and please report back!
Have searched this thread, but nothing came up, so I'm going to post (sorry if it's already been discussed):
If I somehow manage to get my German phone unlocked, or just get a Belgian one (free for all carriers), and bring it with me to Japan, would I be eligible for a SoftBank contract, say, a one-year plan?
I. e., do they give me a Sim-Card, or do they give away contracts only if you get a phone at the same time?
Cheers, dsq.
I have also wondered the same thing regarding carrier policies in other countries (especially when using packets over the 3G network). In Japan, Softbank and Docomo both use 3G networks (for 3G iPhones). Either of these carriers should work with your unlocked 3G.
I do not know the answer to your question specifically, since I could not find anything on their policies regarding "third party" handsets; but here is the link to Softbank's and Docomo's English customer service pages:
http://mb.softbank.jp/mb/en/support/
http://www.nttdocomo.co.jp/english/support/inquiry/
The quickest way to get to the bottom of this is to contact them directly with your question. Trying to interpret policies on your own (that sometimes seem to change depending on who you are talking with) is usually a painful experience in Japan.
Good luck and please report back!