Cancellation

In September, 2015 I was phoned to ask if I wanted to upgrade. I said no and was told that if I cancelled my current contract within, and up to expiry date, of 19thDecember 2015 there would be no cancellation fee payable. On 19th December, 2015 I went in to the Meyerton branch to do the cancellation. I was assisted by a plump lady with short curly brown hair and in a black dress. She made a copy of my ID and asked me to write the note for cancellation on the photocopy page, which I did. My subscription was R229 per month which I made provision for till end of December, 2015. However on 2nd February,2016 an amount of R389.33 was debited to my credit card account. Again on 29th February, 2016 an amount of R329.00 was debited to my credit card. This after I had been into the Meyerton branch again to complain about non-cancellation AND filled in two forms which they requested of me. I am seriously considering laying charges of theft against the company. I went in to Nedbank who told me that they couldn't reverse the payments. Please advise.