but mind you that, most of the provider will ask you to pay $35 for the activation fee. so even you only buying a $20 pre-paid card, you end up paying roughly $55 or so.
also, you need to check if your phone could be working in Canada, as my sister brought in her smart phone, but not able to take the sim card from rogers (not sure why). so end up we didnot buy any prepaid card