Ask the senior hotel receptionist.

First of all, learn from your own mistakes and don't make the same mistakes again.

Secondly, if the guest only booked a room for three days, you can confirm with the guest one by one in the third day's reservation to see if any guest canceled the reservation because of changing the original schedule. This situation is also common in hotel reservations. If there is a cancellation, then the problem of that guest will be solved.

Thirdly, if the reservation for the third day hasn't been cancelled and you really don't have a room available, you can cancel a guest's reservation on the third day, but at the same time, you should help the guest book a room at the same level as your hotel, then call the guest and tell him that it is acceptable to cancel the reservation, and then tell the guest to help him book a room at a hotel. If the hotel is sincere enough to bear the price difference here, the guests will be more satisfied.