OFF CASH ADVANCE CORP HARRASSING DEBT COLLECTION UNK, Massachusetts

A man named Simon keeps calling my home and place of work.  He will call for an hour straight and tie up all the phone lines.  I work in a hospital so this is a big deal! 

He claims that he is collecting a debt that I accrued via pay day loans thru Cash Advance.  But can't be specific as to which Cash Advance company I owe or provide me with a Validation Notice. 

I have reported the phone number to the FTC, local police, and work security.  He wants me to pay $684 to pay off this said loan and then send a seperate money gram to obtain a receipt.

I have verbally notified him not to contact my place of employment but he continues to do so.  I have told him I am not paying any debt without a validation notice of the said debt.  And he still continues to call.  

How do you make them stop?  He told a co-worker that he was coming to get her.  He has cursed out other co-workers.  He is breaking all the rules and yet I still can't get him to stop calling... HELP!