Hi Emilie. Fizz's website mentioned this "When you enter the information for your payment method, the billing address associated to your card must correspond to the address you declared to your bank for that card. The right info must be entered in the corresponding fields, and the address needs to be 100% identical." 

"Other cards such as debit cards, American Express (Amex), Dinners, and others are not accepted. Foreign credit/debit cards are also not accepted. You also cannot use the funds from your Fizz Wallet to pay for your monthly plan."

I think you just need to get a Canadian prepaid credit card and you should be good to go.