deducting even though my contract expired

i have been battling to cancel my Cell C contract now for months. My contract expired and they are still deducting my my account. I have called in 30 days to cancel the contract and they explained they cannot cancel it because i missed a month payment. I calmly explained that i was rerouted from the payments division where i made arrangements to deduct everything i owe by the next debit and that they need to note i want this cancelled and not another debit order should go off. the agent would not put down a note to cancel and i asked to speak to a manager which was not available and the agent promised the manager will call me. to date i have not received a call and i see they deducted an extra R113.00 this month 30 January. this is besides the extra they already deducted for the none payment of the previous month which an amount of R577.96 in total was deducted end of December. Why did they deduct another instalment and why did they deduct more when initially my contract is done with them. I am not impressed. i have emailed thrue many request to have this cancelled..i have called and not succeeded.. Are they gona deduct from my account every month? and More?