A complaint

Hi, we own the Beach retreat whitstable and we had this customer book to stay with us today. But refused to pay a deposit, lied about paying it. They then said they’re like to pay in cash We then sent our cleaner to collect it in cash however the customer then refused to hand it over to our cleaning lady.
The customer then said our flat was dirty, with our even entering the property as we would not hand over details unless we received deposit. 
Further more booking.com then allowed the customer to cancel free of charge, leaving us with out our booking and a loss of £333.  we could have sold to someone else.
Our conversation with the customer is available for you to see. 
We asked twice for deposit and the customer chose to ignore this.

Then I called booking.com and have been promised a call back twice and have not yet received. Have also had one of booking.come agent hang up on me.
This is unacceptable.
I’d like to make  a formal complaint.
Regards 
Arif