SHOCKING CUSTOMER IT SERVICE

I had a computer repair done on the 6th February 2024 and while I was there I bought a printer ink cartridge thinking I would need to replace mine at sometime. I then went overseas on the 8th March and returned on the 20th April and after being in the office for a few days needed to replace my cartridge and when I tried to fit it I realised they had sold me the incorrect cartridge. I went back to the shop hoping they would admit their error and just do an exchange for me. The person who was assisting me, Sheldon, first said that they only do exchanges if they are done within seven days. I explained that i bought the cartridge to have when my current one expired. I had my original invoice but he became very defensive as if he admitted he had made a mistake he would have egg on his face. So he refused to exchange a brand new cartridge which he had given me in error and was not prepared to admit his mistake. Then he asked me to take my printer into their shop so he can see for himself that it does not fit and if that is confirmed he will then approach his boss if he can exchange the cartridge. Well he has definitely lost me as a customer and i definitely would not recommend doing business with them to anyone.