I am fed up with this company sending me threateni...

I am fed up with this company sending me threatening letters when I have acknowledgement from them that I paid the account in full when I sold my flat over 2 years ago. I am taking the case to BBC's Rip-off Britain programme as they need exposing for their incompetence and illegal attempts at harassment and extortion. I have tried to contact them on a number of occasions and have a file of letters,emails and records of unsuccessful phone calls. Impossible people to deal with.