Please follow below steps to change the credit card for your subscription.
1. After login your account on Foxit website https://www.foxitsoftware.com/ , go to My Orders
You will be able to see payment option button under Orders.
2. Click on the payment option,you will see credit cards listed, left click on each credit card to change credit card info .
You may also click on radio button for each card to change default payment card.
3. After finishing , click on Submit to complete changes.