Bad experience at Game Store at the South Coast Mall

Went to purchase ink cartridges for my HP printer did show the sale person which printer I require the ink cartridges for, but when I tried the Ink in my printer it was the wrong cartridge so I went back to game to explain and they said if it is not in the original package they won't t exchange the cartridge for me but how do you open the package without destroying the package I have paid Nearly R700 for the cartridge and the manager at Game Store on the South Coast Mall just refuse to exchange the cartridge do not want a refund just want to exchange for the right cartridge They after service is so bad