VODACOM CONTRACT CANCELLATION, NOT CANCELLED

My other Contract ended in May, i called Vodacom to inform them about my contract cancellation in April,since May end ,i am getting billed ( R239 for airtime) the amount i requested to cancel, i called again in June and my monthly payments was supposed to be R1279 , now i am billed some extra charges every month, which now amounts to R1594, this is not on, and not getting any assistance.