Just received my third message from these dirtbags in three weeks.  Very odd considering that I don't owe any debts and have never used any shady lenders like payday loan servicers.  They are polite enough on the message but Internet research shows that they are among the worst of the bottom-feeding debt collectors.  I'm not sure if they are after the previous owner of my phone number, as they don't identify who they are calling, but that seems unlikely since I've had my number for over three years.  I wouldn't recommend interacting with these clowns; they seem exceptionally shady.