Demands for payment and harrasmen of an non existent account

Norman Bissett continually contact me for payment of a Nashua account. I have never had a Nashua account and yet the harassment is constant. Nashua have informed me that they DO NOT do business with Norman Bissett and confirmed that they have no record of me having an account with them. I asked the harasser for the details of the account. What phone number, what date, what was purchased and they could not tell me anything. The phone number they gave me was the number they called me on which is a company phone supp**** by my employer who are a large Bank. This only proves that they are **********.