Just recently had an issues with Booking.com. I made hotel and rental reservations through them for an event I went to. My car rental was for 11:00am, but my flight was delayed and I got to the car rental (Sixt) at 7:00pm. Sixt gave my car away and were sold out. Because I went through a third party, their policy is to reserve the car for an hour past the reserved time. Mind you, I prepaid for the car in full. I contacted Booking, and they said I had to wait until after the reservation return date to open a ticket for a refund. I did that, then they said I waited too long and they couldn’t confirm that my car was unavailable. I tried to escalate, they said our decision is final and the ticket is closed. They haven’t responded since.