American looking for Canadian carrier help....

[Dr. Impossible]

Hey all-
Im transitioning from St. Paul back to Toronto. Current carrier is AT&T, thinking about getting the unlock code and going with a prepaid month to month situation. Are there any month to month carriers like AIO that I could go month to month and add on international calling(family is still in the States) for a few dollars a month? What are some other good carriers pre and post paid? Any suggestions and info would be greatly appreciated.

Thanks

-Doc