@David4025 What you need to start doing is to message the guests when they book or request to book, confirming that there is only one guest coming. "Hi XXX- I see you have booked for only one person. If there will be more than just you coming, you will need to change the guest count to accurately state how many people are in your group. No one who is not listed on the reservation will be allowed to enter the premises, so we need to make sure it's all correct now, so you won't be inconvenienced on arrival."
If they still book for 1 , and show up with more, you simply refuse them entry, they are trespassing. Or, as Kelly says, amend the reservation, charging for the extra guests, and make sure they officially accept it before allowing entry.
A friend here told me his property manager found 17 people staying in his house that had been booked for 6.
I'm not sure why you think you have to put up with this.
