Unjustified charges

On our holiday to Cape Town we were understandably given a dirty car as the drought requires such concessions. I was informed the front left wheel had small insignificant damage by the agent. I accepted the dirty damaged car without complaint or discount. Upon its return I was charged upward of R700 for damage to the front left wheel. I requested they look into this which took weeks and a second call to actually get the process moving. They came back with pictures and insist I pay the bill, I took additional excess cover so I can claim that way however I feel it is a completely unacceptable situation and warn future customers to rather go with a slightly more expensive rental firm as Avis Budget might charge the next 10 customers for this already damaged wheel and make a tidy profit. Great way to keep your initial charges low. Don't fall for it.