To edit your billing information, log into your account and click on "My account" under your name at the top of the screen. Then click "Change" next to Subscription Status and "Manage payment options". You can then select a different card or enter new billing information.
Once you've entered a new card, please remember to select the new card and click 'Update Payment Method'. This should shift the green 'Currently In Use' status over to the new card and you'll then be able select the red 'Remove' button next to the old card. A reminder that this is only possible when visiting our website from your computer.
If you signed up with PayPal, iTunes, or Google Play, you can edit your billing information through those services.