Most reverse call directories charge a lot. 800 notes doesn't charge to post and read posts. 800 notes lets real people post info about scam calls and robo calls. Of course the companies that make the robo calls and scam calls want it shut down.
I do not answer my phone if I do not know who is calling. I always check 800 notes to see who it is.
If multiple people have left a negative review of the number, I immediately block the number.