AFNI Collections agency or scam artists? Bloomington, Illinois

I received a collection notice from AFNI a year or so ago regarding a Verizon account (DSL).  The amount owed was supposedly from some years previous to that, 2006 I believe.  I never had a service interruption due to nonpayment, and I had the same service until I was sold to Frontier.    AFNI told me that Verizon would have deleted any relevant information once they sold the debt, and that Verizon could do nothing to help me.  I still attempted to fight and dispute the collection notice.  However, since Verizon had no records of the matter, I had no way to "prove" that I didn't owe the money. 

After more than a year of trying to dispute the debt, AFNI offered me a settlement amount.  I just wanted to be done with the whole thing so I paid it.  Payment was a mistake! Now I have a brand new collections notice from AFNI for another supposed Verizon debt.  Since I was sold to Frontier over a year ago, it must be another "old debt."  I should never have given this company my information, as I now believe I will be in for endless collection notices from a fraudulent company for bogus debts.