MTN cellphone company

Battling with MTN for the passed 4 months to get my discount on my account activated because for the passed 4 months they've been deducting too much money from my account. My normal balance is supposed to be R409 each month but they've been deducting R533.40. Contacted them in Sep 2015, 1 Oct 2015, 15 Oct 2015, 31 Oct 2015 and again 30 Nov 2015 on all of these occassions I got ref no after ref no and each different consultant guaranteed me that the discount that is part of my contract with be credited and thereafter reactivated. It never happened until the last person I spoke to on 30 Nov 2015 her name was Lindiwe, she even called me back to say that the credit has gone through but what she picked up they never reactivated the discount for the next month. I left at that and thanked her because she was the only one that actually contacted me back to resolve the issue. Well I assumed it was over then I got an sms 31.12.2015 which I get each month for any deductions on my acc and once again they deducted R533.40 from my account. After she guaranteed me that the discount has been reactived. My ref no she gave was REQ***. I have not contacted them back again