Their employees fraud is not your issue. Consult with experienced attorneys.

It may be in the original contacts. Have them reviewed.

Hire an attorney to do a demand letter.

Consult with experienced attorneys. Use the Avvo search tool to find an attorney. https://www.avvo.com/find-a-lawyer

Note, You must respond in the legal way and on time with, for example a motion or an answer with affirmative defenses. Failure to do so could...

It may be a scam. Whenever one is unsure, give no information, demand proof in writing (do not give your address or other information),...

More information would be needed. Consult with experienced debt collection defense attorneys. Use the Avvo search tool to find an attorney....

Consult with experienced debt collection defense attorneys.

Yes. If the attorney at the firm who was working on your case leaves the firm, you should be told.

This sounds like a scam. Contact the police, state bar and attorney general.