Select the "Auto Payments" tab and click on the account listed to edit

Review Auto Payment Summary for the account to be edited, to proceed to editing click on "Edit"

To change the credit card click on dropdown to select a different card 

Or "Save a Card" to add a new card, and enter in card details

You can also change the amount Payable to Annual or Quarterly Instalments by click on the dropdown 

Edit your debit limit by entering a new amount 

To change Payment Day click on dropdown to select from one of the option. 

Click on "Save" when editing is complete and review Auto Payment Summary