Merc ML63 Schock Absorber

We bought a NEW shock, to find out it doesn't work and was faulty. We were up and down there 3 to 4 times in order to get what we had paid for (if it's so called NEW spares, you shouldn't have to try 3 to 4 times to get a part that isn't faulty or is working). We finally got a NEW Shock that was working. It has been 2months, car hasn't even done 2000KM and Shock is gone. They say they don't Guarantee the parts (who doesn't give Guarantee on so called NEW parts, shows you how much confidence they have in there products they Supply). Now I am sitting with a Shock that can't be used.