To change a credit card associated with an ongoing service, follow these steps:

1. Go to the My Services page and log in with your Yahoo! ID and password.
2. Locate the service for which you want to change the credit card and click the "Service" link.
   You will see Service Details page that displays the credit card information that you use for the purchase
3. Click "Change Payment Method."

You can also access My Services page by clicking "Manage My Services" link on the Yahoo! Wallet page. You will be required to log in using Yahoo! ID and password.