Can I buy iphone 4 in us and use it in canada?

[Lol]

Im travelling to san francisco in two days and my cell phone carrier Rogers are closed so there is no way of buying it before my trip. I already have data plan with Rogers and i was wondering if i can buy an iphone 4 in US for price of 159 which is the 3 year contract price here.
is this possible?

 

[RP]

since you already have a data plan, buy and replace the sim-card. Nothing else needed