Bad services MTN

I paid up my mtn contract to change to prepaid i was a very good client never skip my payment then Last year june o decided to payoff my contract to my suprise somoene did not do their job at MTN n blacklisted me on itc, im so angry i have never defaulted my accounts because i hate itc, i have send proof of payment n MTN comfirmed received my payment n changed my account to prepaid but on the other side they blacklisted me now i want to buy a phone to onother service provider they say mtn blacklisted me im so fedup with MTN i wont advise anyone to use it, n i want them to remove my name