Unprofessional !!

I paid up my account , I requested for a paid up letter .they said it’s been requested I will receive it within 14 days . It’s already a new month I call in they say oh mtn must send the paid up letter . I call mtn , mtn says no Nu debt must give the paid up letter . I call in again to Nu debt just to let the agent hang up the call . I call in again and another agent says that she will request it . also the balance has been paid up it’s a month and mtn says it still shows the balance with them ? So what are you guys not doing your job ? Because it’s affecting my credit score ! . Very rude and very unprofessional.