What do you mean by advanced payment Laura? You can only pay your tab off each month the amount it has been set at or all at one time before you upgrade or leave Koodo. If you want to make the lump payment you can do so through your self serve and pay it with your next bill or pay it at the time you upgrade to a new phone at the Koodo kiosk.
If you're paying via online banking simply pay a little extra each month until you've got enough credit built up to satisfy your tab, then pay it off. It'll require that you read your bill each month and pay enough to cover your current charges plus the extra as the system will just take the amount owing from your credit balance.