Booking.com bad service

I did a booking with booking.com,The total amount of the vacation was R16000 a payment of R8000 was made on the 19/03/2020 and I received a confirmation no : *** - The booking was for the 15 Dec to the 19 Dec 2020. The problem is I had to cancel the booking as I have been badly affected by covid and I will no longer be able to pay the balance now they are saying they will not refund me anything from the amount that I paid. Please assist as I do not understand why wont I get the money back