If in-fact this was a real debt (which I doubt) the statute of limitations in most states is around 4 years. SOL starts with the last received payment date. Even admitting to the debt will not reset the SOL…only another payment activity can. If they do re-age it…then they are in violation of the fair debt and collection act. If you tell them that you have absolute defense of SOL then any threat of a law suite (because they can not legally take action at that point) is a violation. The collector can be fined $1000 for each violation of the FDCA. Threats of law suits (even for those debts still within the SOL), without the true intention of a law suite is also a violation of the FDCA. It is a violation if they say they are from a law firm when they are not. There are a plethora of violations they can be fined for (there are a few below). I would record the call…save written communications…and once they have occurred enough violations (enough in violations that it out weighs the original debt) then I would turn around and sue them…to include reasonable attorney fees.

§ 807. False or misleading representations
A debt collector may not use any false, deceptive, or misleading
representation or means in connection with the collection
of any debt. Without limiting the general application
of the foregoing, the following conduct is a violation of this
section:
(1) The false representation or implication that the debt
collector is vouched for, bonded by, or affiliated with
the United States or any State, including the use of any
badge, uniform, or facsimile thereof.
(2) The false representation of—
(A) the character, amount, or legal status of any debt; or
(B) any services rendered or compensation which may
be lawfully received by any debt collector for the
collection of a debt.
(3) The false representation or implication that any individual
is an attorney or that any communication is from
an attorney.
(4) The representation or implication that nonpayment of
any debt will result in the arrest or imprisonment of
any person or the seizure, garnishment, attachment,
or sale of any property or wages of any person unless
such action is lawful and the debt collector or creditor
intends to take such action.
(5) The threat to take any action that cannot legally be
taken or that is not intended to be taken.
(6) The false representation or implication that a sale,
referral, or other transfer of any interest in a debt shall
cause the consumer to—
(A) lose any claim or defense to payment of the debt;
or
(B) become subject to any practice prohibited by this
title.
(7) The false representation or implication that the consumer
committed any crime or other conduct in order
to disgrace the consumer.