Once Again A Fight with Avis when its pay back tim

I rented a car with Avis paid R1250 deposit , returned the car on the 16th of June 2015, petrol filled, car washed and spotless even the guys at collections checked for the scratches and there was nothing. Now the are nbot paying out my deposit and when i call they say they cant help me out if I only have the ID number they need to get my booking number or the card i used, told them that I didnt pay with the card i paid with cash the the lady told me she cant help with an attitude REALLY? And this is for the second time Avis does this when ever I rent a car with them.