Guests have not stayed but invoices have already generated

Hi,  I'm very new to this system and this is the first time that I have been managing property. 

I have received 4 bookings from two entities and none of the guests come to our property from the bookings. Now the system shows that they have stayed and invoices have been generated automatically.  What to do now..? I think it was spam cause the same person booked the consequence 3 days but did not come to our property.