VW and Audi South Africa wont refund

On the 12th of January 2016, I bought a mechanical part for my Audi at Motorsport Tableview VW branch. The next day I tried to return the part and get my refund as I did not need the part anymore but was told that the part is non-refundable because its cost is below the refundable cost of R270!! (The part I bought cost a total of R293.32-invoice number 653405) <br> I was told that this was an internal policy!!<br> My question is:<br> 1. On my invoice, only electrical parts are not returnable. Why is the other terms and conditions not mentioned?<br> 2. Why would an internal policy affecting customers be not made public?<br> 3. Why would VW/Audi not refund parts that are less than R270?