Beware of Economy Car Rentals - they are not what they claim to be!!!

I recently booked a rental and I had to collect it at OR Tambo airport. When I did the booking I had to pay a deposit of R3 589.76 with a remainder of R5 644,80 on collection. When I arrived to collect, I met the agent, we completed the documentation online, and when I had to pay the outstanding balance the transaction could not go through. We tried several times without success and eventually had to cancel the booking. I copied the agent's detail and also kept a slip of the unsuccessful transaction. She mentioned that I could claim back my deposit and will get a refund. When I contacted the company they refused the refund due to a "no-show". This after I actually arrived at the pick-up point, completed the booking, etc. They closed my inquiry and now I've lost my deposit. Being a pensioner I can't afford not to get my deposit back.