Suppose a guest who has booked a room comes to a hotel and is told that there is no room, but he doesn't want to stay in another hotel. What should I do?

Let's see if your hotel has checked out on the same day, but there is an extra full-day room rate (everyone in the hotel knows). Generally, such rooms are reserved for the night, so clean up such rooms for guests. Explain and apologize to the guests.

Secondly, if there is really no room, then book the nearest hotel for the guests and reimburse the taxi fare, because it is the hotel's fault, and apologize.