airtime dissapearing

My name is Shahieda and a long time mtn customer. Almost 2 years ago I rep**** yes to an airtime subscription and been having problems ever since... What t's me off is that recently my airtime has been going missing... 1st time R68 went missing, 2nd R29.80 and just yesterday R28 something. I know I haven't subscribe to anything because I know the exhorbitant fees deducted when doing so... I keep calling 173 but somehow I never get through to a consultant...no more option?! Last time this happened I never got airtime back... They refere me to Altech Autopage because of this subscription but its a shared call and calling from my cellphone more airtime is used. I just loaded a R30 airtime again and wondering how long it is going to stay like that. I need all airtime back!!! This can't go on.