Are you trying to update the credit card? To make the change login to My Account, Payment Tab (https://selfserve.publicmobile.ca/Overview/payment/Make-a-Payment/) and then click Manage My Card and the Replace this credit card. Then you can enter the reenter credit card information with the new expiry date there
Or if you meant you want other method of paying, one way is to get a voucher from Retails and load the voucher into your My Account or via *611. To load via My Account,, go to My Account, Payment Tab, One Time Payment (https://selfserve.publicmobile.ca/Overview/payment/Make-a-Payment/) and select Payment Voucher as the Payment Method
