VW MIDRAND NO CUSTOMER CARE

VW Midrand the worst service. I mistakenly bought a part which i never collected the following day i went back to advise the sales consultant that i bought the wrong part, the sales person advised me to speak to the manager advised me to buy the correct part and will refer to head office motivating that i bought a wrong part , now three months later i am advised the part will not be taken back. what am i going to do with the part and i know nothing of the part. why was i advised to buy the correct part to motivate it was an error don