Undue harassment by Norman Bissett and Associates

Never have I thought a company can be more inept than government. I was contacted by them over an account I had with Altech Netstar - who by the way also deserve a less than friendly review. None the less the amount was not enormous so I decided to pay. Payment made on the 28th of October 2019. Numerous calls and e-mails from them on when will I pay ensued and eventually there is a shortfall, this is now after I paid the amount in the letter of demand. Finally someone clued up spoke to me and I received a paid up letter on the 11th of November 2019. Ever since that day, almost daily, I get calls from them trying to ****** money. I have sent them on two occasions the very same paid up letter and told them the matter is settled - yet they continue to call. The left hand does not know what the right hand does at Norman Bissett and Associates or they are employing a troupe of illiterates.