In the U.S., the Federal Trade Commission can prosecute companies for unfair business practices: https://www.ftc.gov/about-ftc/contact

Complaining to your state's Attorney General might also be effective, depending on state law and your AG's priorities with regard to enforcing it.

If you can prove you suffered actual damages due to a fraudulent job posting, you could probably go after the company directly, either as an individual plaintiff or as part of a class action.