Faulty Audio Interface

I bought an M-Audio Air 192/4 audio interface on 21 November 2024 at Sunnyside Cash Crusaders (Robert Sobukwe Street), which was a replacement of a faulty Presonus Revelator io24 audio interface. Today (11 December 2024), I went back to the shop to alert them that the M-Audio is faulty again, which has a problem when it comes to recording. They took me from pillar to post, refusing to admit that their product is faulty; they ended up using an online recording software. They insisted that the product is recording. I requested an exchange; the manager refused. He said I can go report to my lawyer. I then requested a refund, and they also refused, saying they can only repair the product when their clause mentions credits, exchanges, or repairs. I wanted an exchange or refund, but they refused. I spent almost 2 hours, and the manager and the gentleman who was helping me left me alone. I was then assisted by their cashier because I wanted a reprint of the receipt. The manager is so rude, gets angry when talking to him, and leaves you to attend to other customers without solving your case. I am really disappointed. I am a regular customer at the shop. I have bought more than 12 items thus far; unfortunately, the stuff has changed in the last 2 years. I need a refund because I am unable to use this device. I tested it again using FL Studio; it is indeed faulty; it does not record properly.