Wrong cartridges suggested for their pen.

I bought a beautiful fountain pen from Houtenpen in Sandton a week ago. My mom, who I bought the pen for, wanted blue ink instead of black ink. We like in a small town so we don't have a fancy stationer which means I had to buy the ink online. I contacted Houtenpen to find out what brand of ink to buy so that it would fit into the pen. They sent me a link for ink on Takealot. I promptly bought the ink and waited for it to arrive. It arrived and the cartridges were too short and too fat to fit the pen. Why is it so hard to get correct information from this company. I would like to know why they gave me the wrong information.