Hyundai Sale person not competent - Train please

I sent someone to buy rings for me for a Hyundai Getz 1.3 0n 18/12/2015. The person I sent had sample rings and Piston with him to make it easy and simple for the sales person and also I was coming from 120 km. I did not want to make another trip. I am not sure if Hyundai trains its people, he sold me wrong rings and I had to travel myself. When I just presented the rings, he knew they were wrong and offered to order for me. I said no. I want a refund. I can travel 120 km again. He said the refund will be done in a weeks' time and he took my bank details. Every time I phone them, they tell me Friday. if I don't get refund on Friday, I should call Monday. It has been same story to date. Today is a month later still no refund. Hyundai should tell me if this is how they should treat customers. I need my payment as matter of urgency. I will not make any further calls to this branch but I wont let go my money!