Hi @Domani0
If you accepted a third party booking (contract to BNB rules) you will have an issue, as they don't have to help you - as someone else rather than the person who booked is staying. (see third party bookings in the Help section).
All you can do is contact the person who booked and say as they not have amended the reservation for the extra day their guests have stayed, you will need to consider cancelling the reservation.
Have you got a contact number for the person who booked? If so call them to try and resolve.
Going forward I would suggest you don't accept third party bookings and don't allow people to visit ahead of bookings. There is no reason for them to - they should be able to get all they need from your listing.