You can check and update your payment details at any time by going to your Account page and clicking on the subscription tab.
This will list each card and show you the type of card and when it expires as well as the last 4 digits to help you identify the card.
You cannot modify existing cards but the way you can update your payment details is by adding a new card that will replace the existing card as the default card.
To add a new default card simply click on the Add new default Card button and this will take you to a form where you can add your new cards details.
Once the card details are verified and added this card will become the new default card for subscription going forward.
The old card is no longer referenced, but if you would like us to remove the old card completely please contact support at email@example.com and we will remove it for you.