Bluu Car Rental bad and ****ming service

I hired a car from Bluu Car Rental. When I was fetching a car from them, car inspection was done on the body of the car only... inspection was not done underneath the car... but when I was bringing back the car the first thing they did they went straight underneath the car and sent me pictures of many damages that were underneath the car. They are claimjng that I am the cause of those damages whereas they did not show me how the car looked like underneath before I took it. When I complained about that later on they said that they discovered a yellow paint on the car which I believe there is something they did after the car was dropped as I know what is happening behind the scenes with some of their employees. I was warned about them before I hired a car from them but I ignored those allegations. They knew that they gonna claim those damages from the next client. When the car was brought back they went straight undernearh the car whereas when I took the car I was never shown what was happening under the car. They are threatning me to sign for those damages.