Unsubscribe me

There is something strange and ********** happening to my airtime. I for many times asked Vodacom about this always connected,cos everytime when my free minutes gets finished, automatically my airtime is used to buy another minutes,which I don't remember signing for.even when it tried to call Vodacom for several times,they just gives me awkward answers,cos on my phone when I even try to unsubscribe,it say I didn't subscribe to any anytime connected.so I ask that they unsubscribe me from that