Vodacom App Problem

Dear Vodacom. I am unable to add my data number to my Vodacom profile. I need to add my data number so I can view my balances and top up data. But when I want to add the number it states that the number is active on another profile. How is this possible? I have called Vodacom and no one seems to know why. This is unacceptable. Please assist so I can add my data number to my my Vodacom app.