PENALTY FOR RETURNING GOODS ON THE SAME DAY!

I bought a clutch kit which costs almost R 1300, however, the guy at the counter gave me the wrong kit (I clearly stated that I wanted a kit for a Polo 1.6 comfortline, 2011 model). After realising that they sold me a kit for a 1.4 comfortiline I went back to return it, on arrival they did not even pay attention to me, after about 30 minutes they demanded that I pay a penalty (for returning the kit) of R 650, I disputed this but later agreed because there was nothing I could do!