You can manage payment methods in your account on the Pendulum website.
Log in to your account
To login to your account, go to your Pendulum Account page. If you are not already logged in, enter your email address and password, and click Log in. If you have any issues logging in, see the help article Trouble logging in.
Go to the "Membership" tab to view subscriptions
Below the welcome message, select Membership.
Navigate to "Manage payment methods"
Click into the Address & payment details section, then click Manage payment methods.
Currently you can only have one payment method per account. Click Edit to enter new payment method information.
Once you have entered all required information for the payment method, check the box to Update all of my memberships to use this payment method, then click Add Payment Method.