Vodacom processed upgrade despite my cancelling the contract

I had the worst experience with Vodacom. They are so eager to let you upgrade but does not want to assist with cancellation queries. I have not agreed to upgrade a line as claimed. I keep on receiving promises that vodacom will escalate and investigate since last week but i receive no feedback. I cancelled my contract on 8th February but the person that assisted me did not cancel it seems because i am still billed.