Hidden fees

I made a booking for a property in RSA my home country. The property had an option to pay later and I did exactly that. Booking.com needed my banking details to secure my booking after that they debited my account and I incurred some unusual international exchange rate fee. This is not the first time I have been charged a exchange rate by Booking.com. Surprisingly I was never charged this fee for the past years that I've been booking on the app. This 2 occasions have left me very appalled as any changes where never communicated. I don't understand why I was charged this fee for a property that's in my country and I'm also making the payment in Rands, not any other currency.

Very frustrated customer!!!