@Ivan547 I would most certainly change the name you give your apartment. Having this name will be very misleading to many guests and will cause more problems in the future. There is no need to list it like this.
Emiel has given you good advice as far as pricing for extra guests. Or you could charge the same for 1 or a couple sharing the same bed (but they still need to enter the correct number of guests, whether there's an extra charge or not), then an extra charge for a thrid person.
I have in my listing name "for solo traveler" but that's because I only host one guest at a time. So in my case, it eliminates problems with extra guests, in your case, it will do the opposite, as you found out.
I think you should apologize to this guest, saying that you didn't realize that the listing heading would be misunderstood and that you are going to change it, but pointing out nicely to the guest that no matter how many guests a listing accomodates, or whether it's an entire place, or whether there is a charge for more than one or two guests, he always needs to state the number of guests correctly when he books, as the hosts need to know how many towels and other amenities to provide for the booking.
