We don't have a way for customers to add a new card separate from another operation. That's on the to do list.
What you can do now, if you want to let them switch cards, is to send them the payment or security deposit link from the booking. They'll be able to put in the new card info there and execute the charge.
The drawback of this method is that it will charge the card immediately rather than waiting for a schedule, but at least it gives you a method to handle it for now. We originally did it this way as a security measure to ensure that the card was charged at least once before queuing it up for a schedule, but now know that we need to add more flexibility here.
Once the guest makes that last payment on the new card, you can also go into the security deposit and switch over the card to the new one.
