Unauthorized debit order

I recently requested to close my Vodacom account as I looking to emigrate soon. I called the collections desk in April and I was advised to call a month before the expected final payment of which I did. I called the collections department and I explained my predicament and the lady who took my call told me they have registered the request to close my account. I made sure the account was paid up by the time of the closure. Lo and behold at the beginning of September I saw that there was an attempt by Vodacom to deduct about R100 from my account. I immediately contacted my bank to reverse the payment. As far as I am concerned all dealings with Vodacom were concluded in August. I tried calling Vodacom but according to their system my number is not registered as being a contract account. Can somebody from Vodacom call me and rectify this.