MTN over charge,an deduct more than amount

Mtn has been over charging me for the past 3 mths ,they don't send me statements, I have logged a complaint with the call centre and with ottery hyper mtn, 1-31994****93 is my ref number, I even followed up last week with a call ,telling them that my next bedt order is the 15th, tonight again. That money should have gone for something else now ,when mtn refund me it doesn't go to my debt account it goes to my mtn account. 3 months they have doing this.