Northland Group, Inc Phoney bill collection, for debts that do not exist. Well crafted, huge scam , Internet

I received a letter form Northand Group, Inc.  It was very well crafted.  I am fairly computer savvy, I make my living by way of several internet stores.  I also have a 800+ credit rating.  This letter says in bold letters: "Your past due account balance:  $3,757.38  Your settlement offer $ 563.64"  Pretty slick.  I don't owe anyone a dime.  I am proud of this.  I have a CPA that audits my books every year, nothing is amiss.  What I did:  I called the local State Attorneys office (here in St. Petersburg Florida) and asked how I could report this, as older people could easily fall for this, especially if their spouse or relative recently died - then you are actually looking for unpaid bills to include in the estate settlement.  I then faxed it in to the State Attorneys office, and it is now in the system.  Do this, report it. Don't bother to contact them.