Shocking exploitation by VW Hatfield

I had my 2017 VW Jetta 6 serviced with VW Hatfield in Melrose for the 1st time in January 2019 as my normal VW Lindsey Saker in Craighall Park sadly closed down. I was informed at this time that I required a new battery which was not covered by my service plan and I paid out of pocket for-R4600 later. The day after getting my car back from them ( note there was nothing wrong with my car before the service) a strange light started flashing intermittently on my dashboard and my car felt strange to drive, when I called to try and find out what this would be I'm told that I would have to bring my car back again. Not being able to take more time of work I left it until my car started jerking and lost power on the highway! I then arranged to get my car back to them to find out what they did to my car-after keeping it for 2 days 'running diagnostics' and not giving me any feedback I finally push to get an answer that my engine is misfiring and a cylinder needs to be replaced and would cost R9000!!! So after taking my perfectly fine (and new) car for an annual service 1st my battery needs replacing and they break my engine at the same time!? At Lindsey Saker I took my much older polo regularly and never experienced just shocking service and was never taken advantage of like this!