Its my money, not yours!!

Bought a Toyota corolla oil pump and found out it was faulty....took it back and they will send it in to aee if it is faulty. So it was faulty and it was repaired. In the meantime i had to buy another pump because my client needed her vehicle. When they got it back they couldnt refund me because it didnt have the box it was sold in. Two years later and they still refuse to refund me on the oil pump because of the box they dont have, even though they had the pump all this time. So they told me they can give me the pump but not my money. What am i supose to do with that pump?? Already got another pump from them (that I paid for) to finish the engine overhaul. Got there today and told Hannes (sales person i bought it from) this cannot go on i want my money back. It has been to long now! He even said the time it came back he will get a box. I tried getting a box but to no sucsess. This is unacceptable. We have supported them for almost 10 years now! The two managers at the branch refused to refund me!!!! I have a right to my money!! I gave back your faulty product!!!