NOT IMPRESSED WITH VODACOM

Vodacom advised me to cancel my contract a month in advance which I did and when I cancelled they told me the last payment would be end of June and guess what July they deducted I was told that the cancellation was done but the calculations were done wrong. Again August they deducted money again which I went and reversed. Yesterday I received a call that my account is outstanding, what account are you talking about because I cancelled my contract, no mam your account is still active after 2 people told me the cancellation was done. Do the staff at Vodacom know what they are doing...