Click Company Settings in the upper right-hand corner, and select "Account Settings"
Click on "Billing Information". Here, you can update your address, change the email for the person to receive invoices, and change credit cards. To change credit cards, click "Add Card", enter the card information, and then click Save
NOTE: If you do not click "Save" located at the bottom of the screen, the changes you make will not be saved. Make sure you select "Save" to make sure your changes are logged.
Your next payment will come from the newly entered card.