Bad service that could have costed my life

Took the car for service and I was told they will be closing early for the day at 12:30 I should collect the car before then. I asked will the car be properly serviced if they working half a day? I was promised a proper job on the car. To my surprise after 2 weeks the car had a brake failure and I called them on the 20th of March and I spoke to Gugu who told me that they are fully booked for the day I should bring the car on the 25th. 1st of all that is not my proplem fully booked or not cause proper job was not done on the car the most crucial part which is brakes was not properly checked and the worst was going to happen because of this brake failure. Took the car today and spoke to Derrick who did not see any sense of urgency and to attend to my car and told me to leave it and he will call me back in the afternoon. This is the return job due to their negligence. He is asking me what was done to the car aren't he supposed to check that on their system? His telling me that Gugu is not in she will be coming in later how is that my problem clearly they need to close shop if Gugu is not available.