Vodacom contracts is a ****

I have 2 contracts phones with Vodacom and the first one I have finished paying for but they are still deducting data and airtime money from me,,, I have called Vodacom several times to completely cancel these data and airtime but they promise to cancel it and never do,,,, I,m very frustrated as I have never used these SIM cards but they are refusing to cancel the data and airtime top up on these 2 contracts