MTN and NUDEBT

Since 2018 paid my last amount owing and MTN CANCELLED THE CONTRACT (have the letter to prove)since then at least x2 a year they phone and order outstanding payment and every year we send POP which helps absolutely zero because nothing gets done.Now we have Nudebt harrassing us on behalf of MTN??????Must I come there and show you how to fill in paper work and update?????Now I have more people harrassing me for something that is paid up and cancelled with proof without either MTN or Nudebt bothering to check up on.Next Step is lawyers