Booking.com Did Not Refund My Car Rental Deposit

I rented a car in Bulgaria through Booking and paid a deposit of $600. I was informed that the deposit would be refunded within two weeks, but it was not returned. Since this was under Booking’s guarantee, I contacted Booking. I was then told that the deposit would be refunded within 28 days. I waited, but the refund was still not processed within this period. Booking assured me that they were handling the matter. However, after 45 days, I received a response stating that the case was closed and that I should contact my bank. I find this outcome unacceptable. If I am required to resolve the issue with my bank, I question the purpose of paying a commission to Booking. I expected Booking to provide security and reliability in this transaction. Unfortunately, this has resulted in the loss of my $600. I strongly advise caution when making reservations through Booking.