Rental Car Poor Service

I booked a through rental cars and my booking was confirmed. Came the time to pick up the car at Woodford at OR Tambo International airport, I couldn't get the car. I ended up hiring the car at Avis. What disappointed me about reantalcars was that despite calls telling them I am stranded and I have already paid them for a car that I did get. The told me that I am not entitled to a full refund of my deposit. I felt cheated on and ****med, hence I would anyone thinking of using their services to think twice especially their terrible customer services.