Go to www.grasshopper.com and sign into your account (ensure that you are signed in as an administrator, as users do not have ability to do this).
Once you are signed in, select Settings then Account. Scroll down to the Credit Card Info section and select Edit. The following fields will pop up and you will be able to add new credit card details. When complete, select Save.
Note: If you started using Grasshopper before June 2011 or changed your interface after you signed up, your account may look different. Use the following Legacy interface instructions.
Legacy interface instructions:
Go to www.grasshopper.com and sign in. 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. After inputting the new credit card details, select Save.