To update your phone number or email address, log in to your account. In the Customer Profile Banner at the top right of homepage, select Manage Subscription to toggle to the Manage Subscription page. 

There, you will see a "Payment method" section. Click the pencil icon within the section and then click the "SEND EMAIL TO UPDATE" button. An email will be sent to the email address associated with your account from which you can update your payment method.