You should be able to get a phone card in Canada for international calls; they are sold everywhere else in the world. You can use this with a disposable mobile or at pay phones, which still do exist.
Pay as you go services, whether cheap phones or SIMs, generally do not cover international calling. People coming here will get a TracFone to have a phone, and an International calling card to call home. It works the same way other places I've been. Someplaces have had "Internet" cards for international calling, less expense per minute than traditional cards for voice lines. These are VOIP (like Skype, but through the card issuer's servers rather than Skype's servers), the disadvantage being that the service may not always be available. Than can be an issue also with calling cards, but not between US and Canada.
