Hi @Anita64
Well is it a cancellation or change of booking?
If the guest wants to change his booking he has to request it from his end. From there you can accept the change without any problem or extra fee's.
If you decide to cancel you will be penalized for it or you can ask your guest to cancel although he won't get his fee's to ABB back but you may forfeit the cancellation policy.
So it seems like you'd just ask your guest to change the dates in the booking and accept them and voila.