Defective Toner cartridge

I would like to warn every one that this company sells defective toner cartridges. We bought a black toner from them after printing +- ten pages with it, it started printing black lines all over the pages. I returned to cartridge zone with the cartridge and my printer so that they could do a test print so that they could see what it is doing. Elani Korf told me that she doesn't even know how to use a printer but it was very convenient for her to use that excuse because she probably knows that a samsung printer tells you when the cartridge is empty and you can't print any further, but what she did know how to do is to weigh the cartridge and tell me that it has to weigh 48g so the cartridge is empty. Did they sell me an empty cartridge? I told Elani that it is not possible she told me that they could send it for testing. after it was sent for testing she phoned us and told us that it was empty and that is why it was printing black lines. My husband had a dispute with her. So first question 1) How could some one with no knowledge of printers work at a printer cartridge company 2) what happened to business ethics? So with no refund we lost 800 odd rand.