@Eden123 Unfortunately, there are people who deliberately target new hosts and unreviewed listings to scam free stays. If a guest contacts Airbnb to complain about their stay but still insists on completing it, you can be quite sure that they intended to run this con before they even arrived.
This happens a lot, but after you've had some successful bookings and reviews you'll be less of a mark for it. Next time a guest claims to be unhappy with their stay, insist that they vacate immediately and don't make it optional.