First, make sure you’re logged in as your admin user, or ask your admin user to make this change for you. Only admins have access to edit the credit card information.
Note: If you started using Grasshopper before June 2011 or changed your interface after you signed up, your account may look different. Scroll down for the Legacy interface instructions.
New interface instructions:
To update your credit card info, click Settings then from the Account tab, scroll down to the Credit Card Info section and select Edit:
Legacy interface instructions:
Click My Account in the top right corner. You'll be brought to the Overview tab.
Scroll down to the bottom and click Edit next to Credit Card in the Contact and Billing Information section.