Qantas points a scan

I used my newly installed Qantas App for my first flight Qantas and then, to earn more points booked AirBnB through the App. It was for a home in Sydney. The app showed the total price for 4 nights at AUS1,516.49. AirBnB charged my bank account US$ 1,516.49. This difference in currency results in an ASD$ 830 or ZAR 10,000 extra charge for me. Neither AirBnB nor Qantas can assist me to get my money refunded. I find this an completely unacceptable and wonder how many people have had similar experiences?