Dischem Ferndale

I have been recently diagnosed with diabetes and bought testing equipment from Dischem Republic but when I got home I realized that they sold me the wrong size. When I returned it to dischem Ferndale, I was told that I can't return it cause the box was opened. How else was I going to know that they sold me the wrong size equipment?? They took back the equipment and happy kept the product. It cost quite a lot and because of my illness, I had to buy another one which was opened anyway. Im so annoyed.