Hensonbedges: It should go without saying that I answer HOBBY-RELATED questions, but I'll make an exception for you.
ASSUMING YOU HAVE EVIDENCE OF REVIEWS FOR PAY (and that's a big assumption), AND a website refuses to address your complaint, AND you're injured by reviews for pay, the following are some options:
1. You could post a review of a product setting forth your evidence of reviews for pay. I'm thinking a derisive video might gain attention. Maybe you can get your friends and family to do the same.
2. You could muster your evidence and file a complaint with the FCC (Federal Communications Commission, the federal agency that governs websites) here:
https://consumercomplaints.fcc.gov/hc/en-us
3. You could sue the website in federal court for fraud, and probably violations of federal statutes.