Bad service and selling second hand broken products as new products

Bought a airflow meter for a mazda mx6 from them. After getting the meter I had no chance of installing it as I was not home then. When I saw the airflow meter after opening the small box with the item just wrapped in bubble wrap I could immediately see that it was not a new airflow meter but a second hand one that has nicks and bumps and had all the original stickers removed. Also the item did not come in a sealed bag as airflow meters should come if they are new. But I was desperate at that point and did not mind it being secondhand as long as it worked. But it did not work. Installed it in the car and everything was a mess. Idling was horrible with black smoke out the exhaust. Called a specialist in george and asked him what to do. Reset the ecu and its even worse. Unplugged the airflow meter and it gets better. Put back the old one and idles fine. Reset the ecu again and plugged in the new second hand one and back to horrible. Tested it on a ohm meter and readings are incorrect. Called them and told them the item was faulty and they won't replace because 7 days have already passed. Fine the 7 days are past but does selling a broken second hand item still qualify as a new item? Closest place for me to do diagnostics on the car is george and that is 170km away. So how am I anyways supposed to get there and back and off work and the part back within 7 days. Highlighted all the reasons they will not do a refund on the invoice. They saw me coming and took me for a expensive ride as paying R2000 for a broken second hand part is daylight robbery. Don't buy from them as they sell second hand stuff as new ones. I am not the first to complain. These skelms should be closed down as they rip people off.talked to rashied and all he says is no replace as its after 7 days. Contacted and notified them on day 8. Won't go the extra mile to help people just going the extra mile to rip people off. Don't support them. EVER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!