Ink cartridge Failure

I ordered a special pack cartridge from them. months later when i needed to use the second black cartridge my printer did not want to read the chip. I contacted them and advised them, and it took almost a month to assist in sending a new cartridge (the back-and-forth courier was at my cost) the new one they sent didn't work either. I am battling to get them to assist with this. i requested that they send me an original cartridge on their costs as this has inconvenienced me. My daughter needs to write her exam and they don't seem to understand the urgency of the matter.