Money taken, yet no room in guest house

So during the past holidays I made a booking a booking through AirBnB for a room with 2 beds at a guest house in Capetown for 4 nights. They (AirBnB) were very quick to debit my bank account. They sent me an email confirming my booking, however upon arriving at the guest house the host (guest house) informed me that they were fully booked and did understand how my booking could have gone through. I was asked to cancel the booking and try another guest house. The same problem occured when I drove to the second guest house. My bank account had been debited for the second time and the second guest house too was fully booked eventhough I had a confirmation email from AirBnB. I frantically went the manual way of driving to guest houses to check availability until I eventually found a room to stay for the night and the next morning had to go through the manual process again to find a room for the remainder of my stay. I did not enjoy my stay there simply because AirBnB is such a ridiculous online booking system which is quick to debit accounts without first confirming availability with the host. To make matters worse, it's been 2months now and still in the battle to get my money back. According to them, they have a ridiculous cancellation policy which now says they are entitled to an excess of R400 of the clients money (being me) if the host (guest house) is unable to provide a service. How stupid is that? I plan to spread the word until people stop using this online platform. It is a *******..