MTN has failed me

My account was handed over to nudebt i paid it up and when i ask MTN to give me a paid up letter I'm told by masilela S that Mtn can't provide it until Nudebt sends my payment File. Shirley S even failed me too I told them that i don't have a contract with nudebt i have one with them, that i have played my part i paid them i need my paid up letter. I don't know why is MTN afraid of Nudebt/Regan M. just to tell him or her our customer has paid please send us the file. She wants a paid up letter. Regan Mckay doesn't even respond to emails. I just need my Paid up latter that's from Mtn because i had a contract with MTN not with nudebt. MTN is refusing to grant me one.