You need to do a search for "employmenty lawyer" or "wrongful termination lawyer".
Based on your facts above you have no legal claim, but perhaps additional facts would change the analysis.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Mr. Doland is correct. There is no legal basis to sue your former manager for talking to others about your termination unless this person defamed you by making false statements of fact which are understood to damage your reputation. If you think this is what happened, talk to an employment law attorney in your area.
They say you get what you pay for, and this response is free, so take it for what it is worth. This is my opinion based on very limited information. My opinion should not be taken as legal advice. For true advice, we would require a confidential consultation where I would ask you questions and get your complete story. This is a public forum, so remember, nothing here is confidential. Nor am I your attorney. I do not know who you are and you have not hired me to provide any legal service. To do so would require us to meet and sign written retainer agreement. My responses are intended for general information only.
I must echo the good advice of my colleagues. You have no case based on the facts you have stated. Furthermore, suing the manager personally would likely be a case without sufficient recovery to find an attorney who would be willing to handle it.
If you feel strongly enough about it you can try suing in small claims court, but you will likely not prevail if your facts are not any better than stated here.
Good luck to you.
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