contract has been re activated

My contract with Cell C has expired 2010 and I cancelled it, and they have been debiting My Account from 2010 until now, of which I tried to explain my problem with them on Thursday 07 -05-2015.they told me that my account has been accidental been reactivated and they have been taking R50.00 from account for the past 4 years and that point I wasn't receiving any Air time for that since my contract was TOP UP .When I ask the to reimburses me they told me they will come back to me with some sort of solution. They never come back to me.Please help me to resolve this since the last debited my account in April 23-04-2015