pre-paid? I'm traveling to Canada for about a month. I'm a extremely heavy data user and will be using for minutes (business IT use) so I thought it would be smart to have 1 month of service and a $35 activation (they will do it if I own the phone no commitment) VS two thousand dollars or more with AT&T roaming (.59 cents a minute! and then texting...)

I have unlocked and jailbroken my iPhone 4. I know it works just fine with a pre-paid service (assuming I cut the sim just right) but that's not what I'm going for. I know the AT&T iPhones IMEI code, etc. are associated with AT&T and I don't know if Bell (or Rogers) will allow me to have a legit plan with them. This prompts the question if I should buy a factory unlocked version (about $660 Canadian Dollars) from apple.ca/retail and have it shipped to our Canadian office from apple.ca and activate it when I get there. Also, I was hoping it was backwards compatible being factory unlocked back to AT&T when I get back.

Also, I could sell my US AT&T phone assuming it's backwards compatible.

If anyone can give me an answer I would appreciate it.