I think there is a reputation restoration company out there, sometimes it is advertised on the Rush Limbaugh Show. Heard it does a good job I hear.
The reputation restoration offers are to suppress negative reviews and maybe clear up some erroneous history (I had a tax license and have been erroneously listed under all sorts of business categories, that license is long closed).
This is outright fraud perpetrated by hostile forces.
You could take them to court for libel and slander but it’s the internet and not likely to result in much criminal prosecution (even when former employers are being harassed).