If you cancelled within 40 minutes, then it's almost guaranteed that Air Canada didn't actually charge you for the ticket in the first place, so there's nothing to be refunded.
When booking a ticket, the airline will generate a pre-authorization against your credit (or debit) card. This will generally show against your card as a "pending transaction", and whilst it will reduce the available funds on your credit card, the amount has not yet been charged.
Then, a day or so later, they will issue an actual charge for the amount, using that pre-authorization as a reference. It is only at that point that the money is actually charged to your credit card.
If you "void" the ticket before that charge (which is what normally happens when you cancel the ticket within 24 hours), then the airline simple never completes the second part of this process. The pre-authorization step occurs, but the charge never does. A few days later the pre-auth disappears, and it's as if it never happened.
If you're using a debit card the process is basically the same, except that as there's no concept of "available funds" other than the actual money in your account, it will appear that the money has been taken from your account - but at that stage it's just the bank reserving that money for the future charge. When that charge never comes, your bank will return the money to your account when the pre-auth disappears a few days later.
As they've said, the pre-authorization will normally disappear within 72 hours, at which time you'll get your money back.
The difference in the way such authorizations are treated is one of the many reasons that it's recommended to use credit cards (rather than debit cards) for transactions like this if you have one.
