Discovery Vitality Systems inefficient and faulty

I cancelled a Vitality membership several months ago but Vitality has been drawing the monthly subscription every month since then. I tried calling the call center to rectify but I apparently FAILED the security questions. My office number, cell number and residential address! Clearly THEY have the wrong details, when I gave them my correct telephone numbers and address last year when I joined up. II have been told I have to update my details on the system!!!!! When the error is theirs! and the OTP does not come through!!!!