Dishonest selling of faulty parts

Seller advertized good working second hand parts. When visiting shop, parts were sold to us, knowing full well that is was rubish parts, which we obviously did not know at the time. Overcharged firstly, paying R1425 for clutch kit and consentric arm, afterwards found out, same parts new cost the same. Contacted seller, which confirmed over charge, and offered to pay a fee back for over charge, which still has not been done! In the meantime the expert that has to do actual install of parts, confirmed that parts are not usable, and could not be fitted, and that we have been sold faulty parts. Contact seller again, made arrangements to return parts, as it says on invoice, can be returned in 48 hours. On arriving back at the shop on Saturday, it was not even open as arrangement. Went back again this morning, to find sales person is not there, and manager/ owner refuses to refund us for useless parts. In total we drove there and back 6 times, full tank of petrol wasted! We are treated like we are stupid, and treated horribly, with aggression, which forced us to leave.. Still have broken parts, car cannot be fixed at mechanic, and without refund, cant buy new parts! *****ed!!!