Unhappy at paying full price for Club V for my foster daughter

I tried for months to get my foster daughter added to Club V at Constantia, even though I showed them a letter from Discovery confirming that she is our dependent and a member of Vitality. What annoys me is that I am currently paying full price for her (R145) instead of receiving the half-price benefit for Vitality members. I have tried to talk to the sales staff at Constantia Virgin Active, and while they have been helpful, the matter has still not been resolved. I do not see why I should be paying full price when our foster daughter is a Vitality member.