No refund

I went to Kia Motors to buy parts on Friday the 29th May 2020. I asked the sales person that if the parts are incorrect, can I return them? He said yes and he explained to me that I will be charged 10% handling fee. I did not have a problem with this. I then asked if they do open on Saturday, and he said yes. I went to my mechanic the next day and he said it is the wrong part. Went to Kia Fourways around 10am. To my surprise, the parts department did not open. The following week, I returned the parts on Wednesday the 3rd of June. They told me that they will not be working for the rest of the week. It will be processed on the Monday the 8th. I have been following up since, and to date, I have not received my money back. Today is the 18th June 2020 and their response is that they are waiting on Head Office.