Vodacom failing to cancel my contracts.

I had four contracts with Vodacom, one for my dad, my brother, wife and I. Two contracts have expired and I informed vodacom to close them in May this year. It's now October and the contracts have not been canceled. I called them from May and everytime I did they would say that they would cancel them beginning of the next month. It has been almost six months without these contracts being canceled. I went to the vodacom store countless times to get help there but I was informed to call the vodacom customer care cancellation division which I did numerous times. My attempts have failed. I have however reversed two payments, one for this month and the other for the previous month. My challenge is that they might blacklist me because of this.