I have an iPhone. On those, you have to make sure the data push is turned off, or it will bill you. I usually made all the calls I needed before heading to Canada, then just kept the phone off up there. Always had free internet on overnights, so talked online or emailed.

It sucks to be in YYZ and pay $2.49 a minute, when you can see NY state from where you are! Stupid Rogers wireless