You may add or remove as many cards as you want by going to Settings -> Payment Method.
I want to change the Credit Card I am using in one of the bookings I made
You may change the Credit Card tied to a Booking by going to Booking Details -> Scroll down to Price Breakdown -> Click on Change Payment Method to select or add another card you would like to use.
I changed my Card and the Promo Code is invalid
There are Bank Privileges all year round. These privileges requires your use of their Cards. In the event that you updated a non-applicable card, you will be unable to enjoy the Promotion/Privilege.
I want to remove my Card from a Booking
The only way for your card not to be charged for a booking is by canceling the booking. If you want to cancel the Booking, please proceed to cancel by going to Booking Details -> Edit -> Cancel.