HI @Ellen395
Unfortunatley there are quite a lot of dishonest people about - and also some guests who think because they've paid money for a place they are entitled to do what they like with it. And then there are some inexperienced guests who just don't realsie they need to enter the number of people staying when they book.
there are probably some strategies you could use to minimise this though
I see from your listing that guests check in with a doorman.
Why not simply state on your listing that ONLY the guests registered in the booking will be able to gain admittance via the doorman and that they will need to bring ID?
when a guest books, reiterate this rule via messaging - say you will need the full names of each guest so that the doorman is able to admit them otherwise they will be denied access.
It''s not foolproof, but the intentionally dishonest guests have a good "feel" for listings they can be sneaky with. A few obvious statements makes them think it's all too hard and they move on elsewhere.
Just a thought.
Good luck!