The Billing section is where Account Owners manage the billing preferences for their GAIN account. This section contains Credit Card information, Current Plan, and Billing History.
To update your Payment Method simply enter your credit card info by clicking on the Add a credit card now button.
Once you have a valid credit card entered you can upgrade or downgrade your subscription plan at any point. Simply select your desired plan and click the Change Plan button.
Note: This action can only be performed by the account owner.