Poor ,Unsatisfactory and Customer Negligence

I took my car for a full service on 24th December 2019, requested for the brake pads to be replaced as they have had a squeaky sound for over 2 months, as well as the reverse camera cap to be fixed, I was instantly told that the reverse cam cap will take long so it won't be fixed as the 24th Dec was a short day. Thembi the service advisor called me to say the brake pads won't be replaced as they were still fine and in a good condition, but they will get them polished. The very same day around 2:30 when I collected my car, right in their premises they still had the same sound. I then booked my car in for brake pads and reverse cam cap on the 21st Jan 2020, I dropped off the vehicle at 7:30 in the morning, signed docs with Thembi she said she cannot confirm if the brake pads will be replaced since the is no faulty sign on the computer box. At 12:05 Thembi called and advised they were busy on my car, she didn't say confirm whether the brakes will be replaced or not. Around 1:10 I called her to advise that I needed the car at 3:30 when I knock off, and that I had a business meeting in Alberton at 4:30,but she was not available and I left a message for her to call me, which she did not. At 3pm I called back she then told me the car will be ready at 4:30, which means missing my meeting. The driver fetched me at 4:35 but to my surprise my car was not touched at all. The reverse camera cap still not working, the brakes started a sound when I reversed a few km from the workshop. I was not given any invoice to show the job done on the vehicle. Thembi said she will call me to let know when I can bring the car back in. When I drove back home, the vehicle rolled when I hit the brakes and not sure what they did on the car since as it wasn't in the condition when I left it in the morning. I called Thembi today to find out what job they've done on the car and why was the reverse camera cap not fixed, she rep**** that the braked were polished "again" and that they will have to strip the car to check why the reverse camera is not working, but they had my vehicle for the whole day and was never attended to. This is disgusting for a big dealer like the lifestyle centre in Bedfordview as its one of the biggest Mercedes Benz dealerships. They do not consider my safety as a customer, malfunction of brake pads may lead to serious accidents. This is poor and unsatisfactory customer service, putting me the driver at a high death risk.