MTN is the worst

I have had a horrible experience with MTN. I had a contract with them. I payed it up for 2 years as was the contract length. Then as I was checking my credit score I realized that the had a not saying I had defaulted on the contract. I then gave them a call. They told me that I had to pay that defaulted amount and the issue would be resolved. I did exactly what they asked me to. I called them about 4 more times trying to clear my name. The last conversation I had with their call centre. Was not pleasant at all as they said to me that MTN had a legal status against me that would not be cleared because of how I was paying my contract. I paid for every single month of my contract. Now they are holding me back from getting more credit because the simply just want to ruin my life. I am livid