Sick and Tired of Cell C

I cancelled my contract with Cell C. Yet I received a call from the retention department stating that I am paying R285. 00 for 5GB Data Line which is a joke as I have cancelled. Yet the caller advised me that no my contract is active and it is not cancelled. I have instructed my bank to allow 1 more debit from Cell C on the 27th June 2019. I will then stop any payments to Cell C after that date. As my Contract is cancelled. I will also be lodging a complaint to the Ombudsman and Icasa for unfair business practices.