Payments

Hi , 

I have received and invoice for 1710 Ron, for which I need to pay the discount for Booking . 
The problem is that the guest didn’t arrived at the property because I tell him the property is all ready occupied and he needs to cancel the booking he made . He didn’t, and the payment method was to pay at the property so he shows in the app like he was stayed and payed for the period. 
I have the messages sent to him to cancel the booking and the response from him telling he will cancel it . 
How can I resolve this because I don’t want to pay the discount for no reason.