MTN has messed up my life

In January I decided to pay off one of my 3 mtn contracts. I went through the process, got a settlement amount and paid r14600. IT turns out someone in the billing department thought that I was paying all my accounts in advance, but they, later on, realized I was only paying to close off one of the accounts. Then after three months of no billing (I never realised mtn wasnt debiting my account), they suddenly took a total of 2700 from my account. I reversed the debit order, went to the mtn shop and I got the run around with no solution. I called the billing department, they made promises that someone from the credit department would call me and I never got the call. For 3 months this continued to happen as I have described as I refused to organise a payment plan because I was not the one who made a mistake here. Anyway, I eventually succumbed and organised a payment plan 2 months ago and have never missed a single payment. Nevertheless, mine and my wife's cellphone numbers have been suspended because my account is in arrears and I am now recieving threaths that these numbers will be shut down completely now. Each time I call them, I demand to speak to the managers, and I have spoken to Nhlanhla and Melanie but upto now have not recieved a solution