Booking.com Charged Extra After Cancellation, No Refund

I made a reservation for Rome, Italy in February. 3 days before my trip, I canceled my reservation and accepted a €50 cancellation fee, expecting a €150 refund.

When I booked, Booking.com charged a €200 pre-authorization. After I canceled, I expected them to refund €150 and close the case. However, they made 2 more transactions and charged my credit card an additional €330.

In total, the cancellation cost me €530 instead of the expected €150, and I have not received any refund.

I have been in contact with Booking.com for 20 days, but there has been no progress and my money is still with them. Never book through Booking.com! Their customer service does not respond and they do not refund the extra amount charged by the host on their site. It is a completely malicious site!