Europcar Bad service

I rented a car at the airport in Cape Town from Europcar. Collected the car after 7pm at night. The gentlemen at the counter handed me the keys and that was it. I didn't even know where the car was parked. He shouted from behind the desk to go to the other side. It was dark where the cars was parked and there was nobody to help me. Nobody walked with me to the car or did an inspection with me. Nobody told me to go and do an inspection when I collected the car. Not that it would have helped as it was so dark outside I would have seen anything on the car. After a few days I took the car back and there was a little scratch (about 2cm) at the back of the car. Know they want to charge me R6500 to fix something I didn't do. That scratch could have been there when I collected the car as it was not inspected with me (and I collected the car in the dark). Why must I pay for it if they didn't do there job. Very Very bad service