Harassing someone that owes you nothing

This company has been harassing me with 6 to ten calls per day from different numbers, no matter how many times I tell them I don't know such a person, then they say they'll update their system accordingly, yet no they keep phoning looking for this person. I'm not a man first of all which is who you are looking for, I don't know this person but keep harassing and harassing non stop, I don't get anything done, because of the number of calls, I cannot manufacture that person, nor do I want anything to do with this company, I even had to Google the name and found out its debt collectors, well don't know the person nor do I care to pay someone else's debt so leave me in peace. Not even a lawyers letter stops these people nor do they know what cease and desist means. Disgusting behavior and thats my professional opinion. Go find that person elsewhere.