Poor cancellation service

I have visited Vodacom shop on 28 July to find out when I can cancel my data contracts. I went to Rustenburg Vodacom in the Waterfall mall at 12 September to have both cancelled. Today 4 Oct I found out that it was not cancelled. I was informed by the consultant that I will have to pay again at end of Oct before it will be settled. I am stressing the point outright that I will not honour that payment since I will not be held accountable for the incompetence of their employees. I will instruct my bank not to do the payment