The worst service I've ever encountered

Today my car was booked for the changing of a bulb for my tail light, I got from the lady assisting me in the afternoon to inform me the car was ready but when I got to the dealership I had to wait for over an hour for my car to be completed and when I asked, the car was still being washed. I'm not sure how long it takes to wash a vehicle. Finally my car was ready however when I checked whether the vehicle was perfect, I stumbled upon a huge scratch on my front bumper of which all the guys, responsible for cleaning and driving the vehicle so i could collect it, denied they scratched it. The mere fact that the manager was going to deal with the matter however I'm still not happy because I was inconvenienced, because I'm supposed to travel to clients the next day however I can't because of the inconvenience I have been put through by the dealership