AVIS terrible service and after service!

Upon pick up of my vehicle at Cape Town international airport (Avis) - I was assisted by a lady at reception for my car collection, the lady mentioned that we were given an upgrade of a vehicle not mentioning that the vehicle had a scratch on the rear right bumper, that was not notice by me at pick up nor was there an inspection done with me at pick up as well, the manner that Avis is handing this issue is not up to professional standard due to the incompetence and laziness of their staff members at late shift, I refuse to pay for unnoticed damage by the company at my expenses!