Unrelated Claim

I would like to express my Major concern about the possibility of being forced to pay for a damage in a car that I did not create. I hired a car through Hertz Car Hire at the Cape Town International Airport. I have been using their services for some time now and have never experience this before. I took a car with them and was sent to a Bay no to collect the car myself with my key of cause. I have noticed minor dents scratches but there was no assistance and that's how I have collected my car in the past. When I went to return the car the assistant highlighted a bumper scratch/ dent and said I need to take responsibility for it. I did highlight that I always get a car with such scratches pity I do not get someone that will actually confirm this and now I get an email about a claim that will be forwarded to me. For what? I would like this to be rectified and I would like my name to cleared as I have never damaged or was never involved in an accident with their car. I am very caustious as I also own a car myself.