To change your billing information, choose “Billing” from the drop-down menu that has your name on it in the dashboard:
Go to the “Billing Information” tab and you will see the fields with your information. All of them are editable fields:
Edit the fields you want to change and follow the further steps by clicking “Continue”. From there you can change your credit card/payment information, downgrade to free and upgrade again and you’ll have an option to switch cards.