insurance on missing hub cap

I rented a van in krugerdorp, drove to Howick and wanted to return in pub and there tempest car hire. To drop it off and exchange for a smaller car. At pmb tempest told me I had to drive to bloemfontein to exchangevan.when I get to bloemfontein the back rear hub cap is missing and there damage under the car. I did not hit anything. I and now been bill R14800. For a car rental and there now want me to pay an extra R2000+ on to rental and insurance. I want there to be some resolution a hub cap. Wheel and scratch cost .thousands of rand. ?