THEFT BY UNAUTHORISED DEDUCTIONS FROM BANK ACCOUNT

Been trying to get MTN out of my bank account since July 2015 with regards to a contract which expired beginning June 2015. Had to contact the bank for a reversal of funds ever since August. I even went as far as to put a block on the MTN debit order via the bank for the amount. MTN simply comes back to deduct again by using a different amount. Been keeping all correspondence with MTN, i.e. emails confirming that account has been cancelled and that debit orders will cease. Also have other correspondence with MTN call center agents confirming that no more monies will be deducted as account has been cancelled and the pathetic excuses they use when later being confronted about these ******* deductions. If by all means possible