********** billing

I have been a loyal customer with cell c since 2014, never letting a debit order bounce. I recently went to the bank and found out that they have been deducting R 60 every month for a contract that I had paid up and loading "benefits" on a SIM card that I had blocked and reported as ******. Earlier this year I was told that the contract in question was done with and closed but my calculations show that they have debited me R 900.00 roughly in the time since the contract was done after the 24 months that I paid. I inboxed them on Facebook and a guy called me, don't remember his name. He was rude to me when I asked to speak to a manager and as someone who works in a call centre I did not appreciate the way he treated me as I was the one who was wronged. I want to know how is cell c going to correct this or must I cancel my contract and find a new service provider? I am shocked and disgusted at the level of service I received and what has been goin on as I have had nothing but good things to say about cell c. I'm waiting for someone to do something or maybe this the end of the road for me and this company.