Do you want to take over his account or just pay the bill?
If its the former, you'll need to visit a Koodo kiosk with Your dad and do a transfer of ownership. There is a 25$ fee.
If it's the latter, you can pay via online banking. Add Koodo as a payee and then use his account number as the account . Be sure to label it as your dad's account so you don't accidently pay the wrong bill in the future.