Vodacom taking our airtime

Vodacom is taking my airtime every week, when I call the centre all they say is that I am subscribed to something . I have never subscribed to anything , I do not share my phone with anyone, I don’t have kids that could have done that. I am even afraid of recharging now because my airtime goes everytime. This is happening to all my mates and family. The all having this missing airtime problem. We even thinking of porting to other networks . Vodacom please stop taking our airtime.