To add or change the card on file, please follow its simple three-step process:
First, click your name in the top right and then click the "Account Settings" option.
2. Once on the “Account Settings” page, head to the “Accounts” tab and click on the primary phone number for your account. If you have several, the primary account is the number you set up when you first started the account.
3. Finally, when you are in the primary account overview, select the “Update Card Details” button and enter the new details.
And just like that you should be good to go for your next billing cycle.