No refund or replacement for faulty item

My mother-in-law (lives in Worcester, Western Cape), while on vacation in Pretoria, bought an industrial mixer for her Take Away shop from the above mentioned retailer during September 2014. When se got home and used it for the very first time the ingredients literally flew out! The mixer does not have different speed switches and most important it does not have a cover to prevent this from happening. Her friend who visited at the time took it along and back to the store. A few weeks passed and they contacted here to collect the \fixed"mixer. Only problem was that the fixed one was not the brand new mixer she bought - it was an old and run down one which she did not accept. Pictures was send to my mother-in-law and she confirmed the aforementioned. In the meantime my mother-in-law also bought another mixer as she urgently needed one for the business as specially during December. When contacting the store they refuse to exchange or refund the mixer and they insist that the fixed one belongs to her. We are really frustrated with the whole situation and feels that something needs to be done but we don't know where to start. Can anyone please advise!!!"""