Diabolical & Diabolical !

Took my Smart car for a service last week. Only had it 10 days prior
I'm always very thorough at checking my car. As i had, the following day (after the service) booked in - for detailing, at a detail specialist.
The weekend prior to service, had an initial check ( four eye check) at the specialist detailer , we went round the car, noting down all scrapes / scratches etc and the work needed .
Took the car for the service , once again a quick look round the car and they took their customary video. Got the car back , in the evening, noticed a dent. I raised this with them immediately and they totally denied it was their fault. As it was dark, i reluctantly took the car and checked again in the am with the detailer specialist ( he also claimed that was not there) . I went back to Mercedes, asking to view the video . They wouldn't let me (data protection ) but they said it was evident on the video.
I asked again to see the video, they again refused. So i asked for a still picture ( by mobile) they refused to take my phone. But reluctantly , my service handler, did produce a still to show me. she then claimed as the car was dirty, it was not clear but apparently, my service handler and her supervisor, could see the dent. I could not categorically see anything at all, yes it was dirty - but that does not mean , there was a dent there.
I told my service handler, i'd lodged a complaint that day. she assured me, someone would get back to me in two working days. I looked on the Mercedes website , which said 5 days for complaints ,so i gave them 7 days including weekend. I Still have not heard one word from them.
The detailer repaired the dent . at an extra cost of £120 .