Mercedes Constatia service so unprofessional and pathetic

Car was sent for service at Mercedes Constantia on the 25 May, was taken in after 7 in the morning, was called to fetch at 16.30, car was still not ready waited at Mercedes till 17.30 for one of the service person to go see what was going on, car wasn't even washed yet they claimed it took so long as car was being washed. Yet since then the handbrake does not work and radio switches off involuntary since. Wasted calls upon calls to them, they once again asked us to come again on 29 May just for them to look, said they will order the part and since have never heard from them plus wasting petrol for this up and down unnecessary running around. This is absolutely pathetic service to say the least. We never had this problem at Mercedes by Cresta, we had fantastic service. I question the service done and me as a lady driver am driving without the handbrake now. How pathetic, ********* and irresponsible is Mercedes