How do I change my billing information?
To update your billing information you need to go to My Account -> My Profile -> Personal & Billing Info.
In Home section you change your billing address.
To update your credit card information you need to go to Subscriptions tab.
See the last column of the table and find Update option.
You will be offered to enter your new credit card information.
If you have used PayPal to sign up to RSS Ground you need to go to your Paypal account to update your credit card and other billing information from there.