No refund policy on goods returned

My wife went to gold wagen shop in Randburg on friday, told the guy in the name of Darius that she is looking for a clutch plate and flywheel for Mini countryman S 2012. She was given those parts. When my mechanic opened those parts, they where small and told me right there that they where wrong. I took them back on Monday with the sample, the Luk book their use as reference didn't have those parts, but for older minis, and they even told me that you can only get the ones I want from the agent's. Why didn't they tell us before we bought those parts, as returns have a 10% handling fee. This is a day light *******.