Telematrix is not giving me sleep

I really do not know where to report this matter now Or what is it that I must do to stop being harassed by telematrix..I paid up my account with them a year ago..but each day I open my eyes from sleep it’s their calls and emails telling me I have an outstanding amount I need to pay them..I called their client service they apologise and confirm that I have nothing with them..I will rest only for a day then boom they call again,this time Nombal ground is assisting them 😭 I regret the day I signed up a contract with me,it’s a a prison sentence that one can’t get over with This is a cry for help Can someone please assist me from this bully company I have paid up my account with them a year ago and I have proof They even sent me a paid up letter