Audi Q3 with fault that can't be fixed

I purchased my Audi Q3 as an ex-demo in 2014 for over R500,000.00 - the highest price I have ever paid for a car (being a single mother). Don't get me wrong, it's a lovely car, I was very happy with it - until the car started making a noise at random times, similar to the gearbox slipping, or a hydraulic-type noise. I took it into Audi Braamfontein service department to get them to fix the problem. They kept the car for a few days and subsequently informed me that the car had been tested and the issue has been raised with Audi Head Office and apparently the problem cannot be fixed - some Q3's have it, some don't!! I have asked Damien from the Service Department to put this in writing, I am still waiting for communication from him.<br> <br> I am absolutely disgusted that I am told to ignore the problem - that sudden noise that appears from nowhere and startles my passengers! Is my vehicle safe? What if I want to sell my Audi? No-one will want to buy it. I have been completely let down by what is supposed to be a professional company that is supposed to manufacture good cars. If Audi Q3's are know to have this strange problem then why aren't they being recalled? I'm absolutely disgusted