Ella,  this is not legal.  It is unethical and just not done in the polite society of legal debt collectors.  Only a scammer would stoop to these tactics. And these tactics are becoming more and more common.  If this person contacts you again,  if possible,  get his name as well as his company name,  phone number, physical and mailing addresses,  and tell him you need written validation of his debt claim.  If he asks for your address,  don't give it,  simply tell him that he should already have it.  Then tell him that  you will no longer discuss any aspect of a debt,  only in writing.

Threatened to have me arrested and continually calling my job