Thrifty the ****** of the car hire industry!!!

I hired a Polo Vivo to travel from CPT to the Eastern Cape for the December holidays for a duration of 4 days (from the 31/12/2015 until the 04/01/2016) telephonically and I was referred to the nearest branch but when I got there they told me they did not have the Vivo but would give me anEttios and the rates were the same for both so I would not be paying a cent more. I paid in a deposit of R6 000, and the cost for the car was R1 864 which came with a full tank. I specifically told the sales person I needed a car with unlimited kilos as I was travelling home and was given a contract and told where to sign and I did. When we took the car back before the specified time I was informed I had exceeded the kilos by 3100km and were required to pay R3100 of which would be deducted from my deposit and would be given a chace of R2900. I asked them to listen to the call I had made to their call centre to book out a car and was told they did not have it and the lady I had spoken to has no recollection of such a conversation, and the manager is also giving me the run around. What is going on with these ******* that operate under reputable names only to ROB US BLIND!!!