If you need to update or change the credit card used to purchase labels with ShipStation Carrier Services, you must do so on the Carrier Settings page. The credit card used for your ShipStation subscription is not the card used to purchase labels through ShipStation Carrier Services.
To change the payment method and billing address for your ShipStation Carrier Services accounts:
Click the settings option for the account.
Select Update Payment Method.
Enter your billing details and click Update Payment.
Payment Method is for Postage Only
Your ShipStation Carrier Services billing information is only used for postage purchases. You can update your billing information for your ShipStation subscription and Shipsurance fees in your Subscription Settings.