Audi South Africa is a reap off

Bought a used 2017 Audi A3 at Bryanston audi dealer in June 2019. The stop/start system was not functioning when I bought the car i.e. the vehicle did not switch off when the it was activated and the car was stationery. I recently (January 2020) took the car to the dealer(Audi Bryanston) to have it repaired (As I'm still under maintenance plan) only be told that the stop/start system does not activate because of the faulty battery and according to the battery diagnostics this is because of the lights that were left on( 15 Feb 2020) so therefore the battery will not be replaced. My car lights have always been set on automatic meaning when the car is switch off, the lights switch off automatically so it doesn't make sense. I raised this with Audi customer care and they are refusing to replace the battery which will fix the start/stop issue even though I still have maintenance plan. I'm really disappointed with Bryanston Audi as they sold me a battery that was already faulty (low voltage) and just because I reported this issue recently, now I'm told it's my fault and I have to replace the battery myself. Really disappointed with this experience and they are definitely losing me as a customer!