Most people panic when told there is still a mortgage on the property they wish to buy. Before the signing date at the notary, your agent will instruct the Bank in question to prepare the cancellation costs, the remaining amount and any interest due pertaining to the seller. On the day of the signing you will be asked to prepare a banker's draft for the amount due payable to the bank, which will cover the mortgage etc, the remainder going to the seller.
It is then the banks responsibility to register the cancellation of the mortgage.