What a crazy ridiculous process for Exchange

I have purchased this unit Om OBL EXP BLK at Game store Mall of Africa 14/04/19 and the curtain rail did not fit on my door . My wife took the curtain rail for exchange in Midrand Game and she was confronted by Lettie ( Sales Consultant and Emmanuel acting Store Manager whom advised her that they do not have the stock for this product and they cannot exchange for something else . She asked for refund but she was not helped I phoned and spoke to Emmanuel who ridiculed me and advised that he will not exchange the product and he just laughing over the phone and making me sound like a fool. Please advise all I need is a refund since I cannot be exposed to such pathetic service for my support . What are the process to get a refund ? why Mall of Africa upon purchasing the product did they not advise me that the only store that can exchange the product should I wish to will only be them ? If the store does not have a certain item one needs to go back to original store where they bought the item for exchange if that is the case is a crazy ridiculous idea . Awaiting for urgent feedback with the way forward and whilst on this give Emmanuel And Lettie customer service training since they do not know how to talk to people they both clearly stated that I am making my issues their own and they did not send me to Mall of Africa Game .