Poor management and bad service

Kessel Motor loop street, Cape Town. A month ago I took my car in for service because the engine light was on with a diagnosis I did at Mercedes a day earlier in Century City explaining to them two things that needed to be done on the car, four hours later there call me and tell me it’s something else not what is on the diagnosis report by Mercedes, that it is the Cord that is faulty. I was guaranteed that this is going to take the problem away for R5000.00 which I paid. Two days later the engine light came on again I took it back. That mechanics said to me it’s the exhaust sensor they are going to fix it. He fixed the exhaust I end up paying R2000.00 for the exhaust to be fixed and I they ask me to driver the car for a week to clean out the exhaust, this didn’t work as the engine light came on again. I went back to the garage to ask them what is going on here, the manager Sandra Carbatt ask me if I can leave the car with them for two days to sort out the problem which I agree. I took my car back to Kessel motor on Thursday 29 November 2018 to check their work which I have been guaranteed both time by the manager Sandra On Thursday 29 November 2018 I received a call by the mechanic telling me that full service needed to be done on the car and he said that will cost me R2800.00 for the service, I said to him no I don’t have money and he said he will come back to me with a better price that’s Thursday. On Friday since I did not hear anything from him Thursday I called him Friday afternoon around 1pm and he answered telling me that the service was done yesterday without my consent. I arrived at garage to fetch my car, the manager Sandra refuse to give to car and forcing me to pay for the service done. Service I did not authorize. I explained to her I did not give the go ahead to do any service on my car. This manager was very rude and didn’t wanted to hear anything as she only want money. I ask her about my guarantee for both jobs she did and no answer. I refuse to pay anything as I did not ask for the service, she said she will not give me my car. About an hour later she ask me to pay for the parts only and I said no it’s the garage faulty which you know that your guys did not call me for authorization. She kept me down for three hours I ended up paying because I needed to go pick up my kids from school this is very sad. She say to me and most not bring back the car to the garage as if you own the garage. Very poor management from her side and I wish the owners can look into this problem. This is the worst garage you can ever take your car, no service and they don’t know their jobs.