Unauthorized deductions

I upgraded my vodacom contract from the red advantage subscription (R999 per month) and a month to month 5GB data bundle (R399 per month) to a red VIP contract (R2099 per month which includes a 20GB data bundle) I then cancelled the month to month R399 data bundle as it was no longer needed. Vodacom has however not done this even though I have made numerous calls requesting the same - but nothing has been done and R399 has been deducted ever since. My contract will be ending now in February and I will not renew it. I will migrate to cell C or Telkom.