I took my car in for electronic issues to be diagnosed and repaired based on the diagnostic results

I took my car in for electronic issues to be diagnosed and repaired based on the diagnostic results. This is a separate issue, but to put it simply, he failed to identify the actual problems with my car and just advised me to replace parts that had already been replaced. The main issue is that I dropped off my car with no scratches on the front bumper or on either fender. When I came to collect it, the passenger side of the bumper was loose and the fender was scratched. He denied causing the damage and refused to take any accountability, even though he claims his premises is under 24/7 surveillance and that his staff would never damage a client's car without reporting it. When we requested to view the footage, he told us to take him to court to get a letter of demand. He appears trustworthy, but I've learned not to trust appearances when it comes to my property and his business.