When a customer signs a Pre-approval, they are sent an email to confirm their agreement. This email contains a link to update/cancel their agreement. This includes the ability to enter a new card or bank account.
As a merchant, you can also find the pre-approval update/cancel link by navigating to the payer record and clicking View/Edit pre-approval.
You should copy this link and send it in an email to the payer so they can update the information themselves, however you can also manually update the information yourself if you have it on hand.
Figure: You can find the View/Edit pre-approval link on the Payer Details screen.
Figure: The View/Edit pre-approval screen.