How do I remove and add a dog when I already have a booking scheduled?

We have a sitter scheduled to come in 2 weeks that was scheduled months ago. When we booked her for this trip, we had 3 pups, Binks, Luna and Tucker. Tucker has passed since this booking we scheduled. We have a new puppy, Sammy, which I have added to my profile, but I am unable to remove Tucker because he's included in the stay booked for October 17 - 20. Help!