AirBnb charged me twice and finding it impossible to get a full refund

I booked and paid for accommodation on AirBnb for 5 nights. Later, I looked on my credit card statement and saw two different charges for the same reservation, one pending and one that had gone off immediately. I then realised that the one that had gone off immediately was actually ZAR200 more per night than the price per night that I booked at. I contacted AirBnb with my reservation number via a virtually impossible-to-find means of online chat with a support agent. Two support agents in succession just ignored the provided reservation number and my query and tried to discuss a completely different reservation at different accommodation. Finally, screenshots of the duplicate credit card charges were requested by an "anonymous" support agent (the previous two provided their names). I sent those and a couple of days later: no feedback whatsoever. I see that the credit card charge that was the price I'd actually booked at has been reversed and the incorrect credit card charge - which is ZAR200 more than what was advertised per night - has not. I've basically been ********. I now see all over the internet that these AirBnb dual charges are commonplace and that they are deliberately impossible to get hold of. AirBnb: you owe me ZAR1000 cash.