MTN *****ing my money after expiry of the contract.

I entered into a contract with MTN November 2013, purchasing a Blackberry 9720 with added benefits of data and airtime. Halfway through my contract my phone got ****** and as I had not insured the phone I had to continue paying them. I asked if they would cut the data and airtime but charge for the devise as I was no longer using the number and they said no, the contract is as per the package. I made peace with that. I told them to cancel the contract as soon as it was up because I will not be using the number ever, at which they agreed. As soon as the contract end date approach in the end of November 2015, I made sure I called them to ensure that they cancel the contract because I had heard people complaining about them taking money after the contract has lapsed and telling you that you never called to cancel. They even deactivated the 083 number that I was using. But they still went on and debited my account. I noticed after 3 months of their shenanigans and went to the bank and cancelled their debit order as well as retract the only 2 debits that the bank could from them, that they had taken *******ly from my account. Now they have the nerve to tell me I owe them and harassing me with phone calls after I had repeatedly told them what had happened! This company is just a hub of white collar crime de*****ing people of their hard earned money.