CANCELLATION POLICY FOR FALSE PLACES ADVERTISED

Hi I booked a place on the 31st called the Afropolitan in randburg on booking.com. The place was available and reserved it and money went off my bank account, then 2min later I decided to call so I can arrange check-in. I WAS TOLD THE PLACE WAS FULLY BOOKED. how does this happen when a minute ago on booking.com it was available. So I then went to cancel the booking so I can get my refund, I chose the free cancellation option, but only to be told I am going to only receive 30% of my money!!!!!!!!!! Hell no. Why??? how is any of this my fault? so where is the breakdown here? I want my full refund.

cancellation reservation: ***. Regards Zozo