I guess this is a simple one.

Sorry my manuel is all in Japanese and I am having trouble find some information.

I have been operating under this assumption and now I am worried.

I have no umlimted data transfer package or anything. When the iphone has the 3G logo up it using 3G for data and when it has the wi-fi strengh logo thing up it is using wifi for data. So If I am at home and I can use the net without worrying about a massive bill right?

That's what I'm working on - if you're on your network you shouldn't be sending data by 3G, so shouldn't be billed by anyone other than your ISP.