mtn paid up

i had a contract with mtn and handed me over to mbd attorney it was around one thousand something then i paid but was left with 350.00 then next thing after few months it was R845.00 then i paid it off on the 31 december 2015 since the 4th of jan 2016 requesting paid up,they keep on lying to me everyday even the manage makhosonke i never received anything.now i cant cancel my contract with mtn because the status and i want to clear my credit record.stop lying to me give me paid up letter