Automotive part complaint

I ordered a petrolpump for my Mercedes 3 weeks ago before Easter weekend.I dealt with Nico a salesman at Primapart.I paid R1300 for the petrol pump and took it immediately to Extra mile mecjanics.They took off my old pump and fitted the new one.My car did not start with the new pump.I took the pump back to Prima part as its not working on my car.They send the pump back to the supplier the same day.The supplier is Masterparts im Belville Cape Town.Hennie was handling the query at Masterparts.The mechanic took my old petrolpump and sealed it because it was leaking.I kept on calling both supplier and Primapart but till today the query is still not sorted out.I told them i want my money back as the old pump was repaired.I told them that it is three weeks now and i feel its unfair as this is my only car which i must use to travel to work and back.If my old pump did not want to work it meant that my car would stand for three weeks and i would battle to get to work and back.I feel this is very umfair as i immediately paid for the pump but i am now waiting three weeks for my money.At this stage i dont have the money or a pump.