How do I change (update) my billing information?

To update your billing information you need to go to the  My Account section and click on Profile & Billing section:

In the Subscriptions tab, you need to click on the Update option. You will be offered to enter your new credit card information:

If you have used PayPal to sign up for RSS Ground, you need to go to your Paypal account to update your credit card and other billing information from there.