Some stranger called you and told you that you owe money for some debt?

If that happened to you, did you check your credit report to see if the debt actually exists?  (You can get up to three free credit reports a year).  Did your credit report show the debt was written off, or was the call from the original creditor?

If the debt was written off, that means the original creditor is trying to recover their tax liability, and they have sold your debt to some collector, for pennies on the dollar.  This is usually called a "charge off" or a "write off".

You may still owe the debt!  If you received a call from the collector, your next step is to assure the collector that called is the one who currently holds your debt.  FDCPA rulings state that collectors MUST snailmail (USPS post) a "Validation Notice" to the debtor within 5 days of the original contact.  If you do not get that Validation Notice, the phone call was probably NOT from the current legal holder of your debt.

By law, collectors must not make certain threats, such as sending you to jail (debt is a civil matter, not a criminal matter).  The collector also must not promise to return your credit report to where it was before you stopped paying the debt (the "charge off" or "nonpay" statement will usually remain on your credit report for seven years).

If you owe (or owed) a debt, and if you have been called by a collector, you really need to take some time and read the information here:
https://www.consumer.ftc.gov/articles/0149-debt-collection

You really should pay any outstanding debt ... but assure the payment goes to the legally authorized person or company!