We will be driving through Canada (from Buffalo to Detroit) and staying a little while in Toronto. We would like to avoid roaming charges for Edge/3G. Never having taken my iPhone across the border, do we just need to turn off roaming in the settings, and that's it? We don't expect to place or receive many calls during our stay in Canada, but data is something we use quite a bit. But not at the elevated rates for roaming. So, is it a stupid question, or is there anything else we need to do to avoid data charges? Thanks.