If you want to consult with an attorney to determine IF you might possibly have a cause of action here, meet with a litigation attorney. There does not appear to be tax fraud, but you will want to look at your return again to see if the changes resulted in too large a refund.
This is not intended to be legal advice, and is general in nature.
You need to consult with a local civil litigation attorney first and then ask the tax practitioner why the information was changed. It might be explainable. It might be civil. It might be criminal.
The information provided in this answer does not create an attorney-client relationship and is not considered to be legal advice.