Auto Glen Motors ricks of foul-play!! Day-light robbery at its best - the worse experience ever!!!

I took my car for repairs at BMW Auto Glen Motors. I wanted them to replace a broken vent pipe. The service advisor - Francois van Rensburg then called advising that a long list of other things needed to be replaced. Given that the are the manufacturer of the car and probably know what's best I gave them the go-ahead even though I had reservations because I hadn't experienced any problems prior. I am not a mechanic so I couldn't argue with him or dispute what he was advising. I took his advise on good faith, after my safety and that of my family was ''at stake'' if I can call it that. On numerous occasions before giving him the go-ahead we asked if the car wouldn't be in a worse state once they are done. Francois assured us that all will be well, the car would be much better than before. Long and behold, 40k later we pick up the car and almost a km from the dealership we get a drive-train error message, the gear was shaking etc. We decide to them book the car into Sandton Auto for service and to get a second opinion about the drive train message the day after picking the car up from Auto Glen Motors. To our surprise, Sandton Auto tells us that as part of the service they would be replacing spark plugs etc. - something that was apparently replaced at Auto Glen Motors the day before( Francois had told us that they picked up a misfire and they needed to replace the spark plugs). So we don't say a thing and allow Sandton Auto to replace these. The next day, the car starts leaking oil - something which was never there before we booked the car into Auto Glen Motors, something which Auto Glen Motors had informed us they picked up and apparently attended to it. We went back to Auto Glen Motors, Francois couldn't even explain to us what they did to our car, he had no explanation for the spark plugs which they supposedly replaced - which we were charged for. All trust and faith we had in them is lost, how do we even know that they actually fitted all the new parts that they quoted us on? We had asked them to put all the old parts in our boot - the old spark plugs which Auto Glen Motors apparently replaced where not in the boot. We ask to see Francois's supervisor, we were told we can only see him by appointment and that he would call us back. The supervisor doesn't called us back. So we took the car back to Auto Glen Motors so they can sort out the mess they created. Its apparent that Auto Glen Motors has no regard for their customers, they clearly are doing fraudulent things and cheating customers of their hard owned money (how do you say you changed my worn out spark plugs and the very next day, another dealership replaces them again). Surely if you attend to certain things that are part of the service, you are supposed to update the on-bound car computer such that it acknowledges that with regards to the service only this and that are outstanding? The nerve to then tell us there they don't really know why the car is leaking, it could be this and that - they need to figure out what's what. They don't know when we will get our car back, so we must be inconvenienced whilst they take their time to fix that they ****ed up. The car is in a far, far worse state then when we took it in. Surely the diagnosis test that they do on the car should tell them what's wrong. Seems they follow a trail and error methodology in resolving issues at the expense of the customers money because they end up replacing things that probably shouldn't even be replaced - they have replaced our fan belt, one wonders how that's connected to the broken vent pipe which is what we originally took the car in for. No one should ever take their car there for service!!!!!!!!