Is this slander/defamation?

This answer is not specific legal advice, nor does it establish an attorney client relationship. Generally, if the information that was provided was correct, truth is a defense to a defamation claim. There may be debt collection restrictions on providing this type of information to another individual, but that is a different question that someone more familiar with debt collection requirements could answer.

Get a lawyer to write a cease and desist letter to stop the slander. If that does not shake the person from stopping the slander, sue to protect your rights.

You have rights but you must act to protect them.

Check with a lawyer in your locale to discuss more of the details.

Good luck to you.

God bless.

NOTE: This answer is made available by the out-of-state lawyer for educational purposes only. By using or participating in this site you understand that there is no attorney client privilege between you and the attorney responding. This site should not be used as a substitute for competent legal advice from a licensed professional attorney that practices in the subject practice discipline and with whom you have an attorney client relationship along with all the privileges that relationship provides. The law changes frequently and varies from jurisdiction to jurisdiction. The information and materials provided are general in nature, and may not apply to a specific factual or legal circumstance described in the question.