Instructions
Sign into your Xbox Live account at.xbox.com.
Click on the "Marketplace" link at the top right of the home screen.
Click "My Account" to access your Xbox Live Account options.
Select "Manage Payment Options" from the list on the left-hand side of the screen.
Choose the payment option you wish to remove from the list and click "Remove." The site will ask you to confirm that you wish to remove your payment option. Select "Yes." Once completed, your payment information will be removed from the account.