You can update your credit card details under My Account and the Subscriptions tab.
Please click the Manage button and select Update renewal payment method.
Select Add new card, enter your details and click Create:
Now select the correct card and click Update.
Deleting a credit card -
To delete an existing credit card, please go to the My Cards tab and click the bin icon located on the right hand side of the page and click Yes when it prompts.