Booking.com Flight Reservation Missing Confirmation After Cash Payment

I made a flight reservation through Booking.com and paid 200 USD in cash, but I have still not received any booking confirmation or receipt. Because there is no confirmation, I cannot be sure that my flight has been booked and I cannot access any details about my trip. I have tried to get support from Booking.com customer service but I have not been able to reach anyone or receive any help. Since I have paid 200 USD and have no proof of my reservation or ticket, I am very concerned about this situation. I request that my situation be urgently checked and that a full refund of the 200 USD I paid be provided as soon as possible, as I did not receive any confirmation or usable service from this booking.