Broken left Mirror

I took my car in for a service and reported that the left mirror indicator is not working. When collecting my car the service advisor Hamid Alberts informed me that the same mirror was cracked when booked in. I told him that the mirror was not broken , how will I report iit when it's broken and why the same mirror that I reported. Hamid did not check the vehicle as he was supposed to do. When I confronted him about it, he said he was busy at that stage and checked it after I left. I try to solve it with the Manager with no luck, he said it is not his problem, which is unprofessional from a Mercedes Benz Manager. I insist that they check the camera footage to proof that the mirror was broken. This is unexceptable.... and I will definitely take it further if needed