Pathetic Customer Service

I am so livid with MTN Credit Management Department. I have been on contract with them for more than once and my current contract with them is almost two years (I cant wait so I can get leave them). This started as an incorrect billing ever since they came back from strike, when I refused and questioned the amounts they suspended my line and threatened with legal action, because this was such and inconvenience for me I told them I can never be able to pay the whole amount and I needed my line activated soon, we then agreed on an arrangement of me paying in instalments which I have then honored since then, and my latest payment was, rightfully so, the end of December 2015, and according to my understanding im only left with one instalment which is due end of January 2016. Four days ago my line got suspended,I call 808 they tell me only the credit department can assist me and they will call me shortly to resolve the matter, THEY HAVE NOT. I managed to get an email address, i am very disappointed at the RUDE response. My line is still suspended, they refuse to call me, they now tell me of different amount, after we had an arrangement, how so? Why so suddenly, not even a notice? HELP!