This is a good tactic.
My Long time lawyer knows this well.
It applies to debts you owe other than a mortgage too.
If you have a debt thats been sold (To a collection company - even another lawyer) you have the right to request all documentation proving the debt. If it's old...and better yet, has been sold more than once. Often no one has the paper. End of story.
I wish I had known my lawyer when I was still in my first year of college! He explained that these "bottom feeders" will buy your debt for an average of 20 cents on the dollar, sometimes less. Then they have the full power of the law behind them to collect the balance originally due, plus whatever they falsely tack on and know what? Aside from 20 bucks to file in small claims court if it goes that far...it's all GRAVY.
For example say you owe bank A $4,000.00 for a closed credit card.
Scummy Collector B buys the debt from the bank for $800.00 (20 cents on the dollar) and makes a tidy profit of $3,200.00 plus whatever legal fees and BS they add on. Nice eh?
Not only that, but once said scummy collector buys this debt...you have no more business with bank A. As far as they're concerned the matter is closed. All previously arranged deals are off. They don't know you anymore. They write off the debt. You are left paying someone you never had busines with and its just pure cash the bottom feeders are shaking you down for.
My lawyer helped me whack quite a lot of knuckles for debt owing to an ex and some which had been paid to a prior scummy collector back after HS who was likely skimming from their own company and never reported half the debt paid which was over 2,000.00.
Trust me the money I paid my lawyer which was not that much..saved me a lot of cash and grief. You can do some of this yourself, but the weight of a call or letter from a lawyer often puts these people off cold. Also you no longer have to take the abuse. "Talk to the hand." hope this helps.