@Derek240
Derek, as you have a chunky listing with three beds, I would think it is improbable that you would usually get a solo traveller booking such a big place.
In future, I'd recommend you get quizzing and confirm how many guests are arriving from the get go, when you receive a booking or a request for a low guest count.
Especially if it is one person, I'd think it was surely an error, inadvertently or malice prepensed.
It's best to solve it in advance rather than having a tricky doorstep conversation.
Chalk this one up as experience and good luck going forward.