Cancellation of contract

I cancelled my cell phone contract with Virgin Mobile on 1 September. My contract expired on 1 Oct and I was told to cancel it exactly one month before the expiry date which I did. On the 13 July 2015 (***) I spoke to a gentleman called Andrew who assured me (when asking him numerous times) that my last debit order would be on 1 Sept 2015. I asked him to confirm this call is being recorded should money be taken off after 1 Sept and he said all calls were recorded. Then on 1 Oct I get an about of R149 debited from my account. I phone again yesterday (***) asking why this happened when I was clearly told that no more debit orders would be coming off my account after 1 Sept. I still don't understand his reasoning but he then tells me that another amount of R243.10 will be taken off on 1 Nov. Please advise how I can stop Virgin Mobile taking off money after they told me (and it's recorded) that I would not have any more payments after 1 Sept. I don't understand why I am paying for Oct and Nov (and the amount of R243.10 is not even my contract debit order amount - this has always been R149 standard). I look forward to your reply. Rosemary Hodge.