Factory fault!!

I have had the worst experience with Volkswagen. I purchased a polo TSI 1.6 Rline in 2019. This was a cash purchase. 2022 January the alternator became faulty which resulted in the battery not being charged and the car coming to a complete stop. I took the car to VW Wonderboom and it was fixed and it was still under warranty. 7 months later and I experienced the same problem. My car is no longer under warranty. VW wants me to pay R35000 for a new alternator. They do not know what the problem is and why the alternator keeps doing this. I will have to pay R35000 for an alternator which will then be faulty again few months later because VW Wonderboom cannot tell me what the issue is! This is totally unacceptable. VW sold me a car with a faulty alternator! How is it possible that they do not know what is causing the alternator to be faulty?