You can! Just follow these steps:
1. Log in to your EventSprout account HERE.
2. Click on the "View Order" button for the event which you have a payment plan.
3. Click the "Payment Plan" section.
4. Hit "Update Credit Card".
5. Update the fields with your new card.
6. Click 'Submit'.
Note: If you need to update credit card number, you must complete the update prior to your scheduled payment date.