If they're in the same country, talk to a suitable lawyer. A letter from a lawyer may be enough to get them to stop.

Follow thesuperbigfrog's suggestion too, but don't just link to their pages, quote them (maybe as screenshots so search engines don't grab the bad things) and link to archive.org copies.

Sounds on the surface of like deliberate commercial libel; given the multiple change/revert cycles, talking to a lawyer sounds like a good idea. A lot of companies will respond more compliantly to a C&D from an attorney than to a polite request from another firm.

It’s probably not worth it to go all they way to a court. But I do agree that having a lawyer sending them a letter might be worth considering.

Sounds like a possible legal issue, as mkl said, talking to a lawyer is probably what you need to do.

It happens a lot in SaaS, this needs to stop. I think calling them out on your website will do the job.

Create a blog post that calls out all the misinformation, why/how it is false, and links to their page with the false information.

If they continue to revert back to the pages they are either incompetent or malicious. In either case, you need to get the facts out so that people are not misled.