MTN Cavendish couldn't care less

The Cavendish Square branch was happy to take my money, but when I discovered that they had supp**** me with a defective wifi router, they were a lot less happy to help. I tried to swap it for a functional unit, but they shrugged and said there was nothing they could do because the manager allegedly wasn't available to allow the exchange. "Maybe come back on Monday. Oh, also kiss your cash goodbye. No refunds". Sorry, but that's not acceptable.