Goldwagen selling me wrong stuff and don't want to take it back.

I recently bought service kit for my auris 1.6 RT and they gave me plugs that are not working and the plugs worth R700 and something, when I return them back they told me that they can't take the plugs back because I already installed them in the car but I told them that I didn't know if the plugs are not for the car, so now they don't want to take them, im now stuck with plugs that doesn't work. My name is Daniel Msibi and my phone no is ********** 172