Defamation of character and terrible service!

Due to contact issues there was an outstanding balance on my account in 2014 which I was notified by MTNs legal department about and it was settled I'm still listed on their system as in arrears. A piad up letter was forwarded to them in 2014 and now again. I also invluded customer care that so proudly sent me an email with an 8hr turn around time, guess what it's been 2 WEEKS and NOTHING!! Almost 6years down the line this is still reflecting on their system as unpaid. I have made numerous calls and visits to the store to sort this out and NOTHING! No one phones you back and everyone keeps giving you the same nonsense message that it's been "escalated" to the legal department. It's been "escalated" for almost 6years!! I even tried calling them myself to try and sort it out and was told that I can't be put trough to them and that the customer care agents don't have the legal departments number??? What a load of nonsense! Is this not the same organization?! How do you operate like that! Due to this issue I was denied a contract and humuliated because I didn't know what the consultant was talking about. I looked like a complete idiot! This is unacceptable and borders on defamation of character! To date there has been nothing done from MTNs side!!! If there is no resolution to this matter I'm going to seek legal council. What guarantees do I have that this won't spill over into my credit score?!