Texts, emails, and PMs so if he writes a fake review you can use the communication as evidence. You should cut off all communication with him immediately. It can be a sense of entitlement by the potential client that makes him behave like a jerk. Next time if this happens once you say no, do not engage the potential client.

It happens more often than anyone would like it to.
It's definitely possible to have a fake review removed and the bonus for you is that you have evidence that he threatened it.
So yes good into the info.
You might also like to name and shame on the providers only board  
If he's willing to be such an asshole for not getting an appointment I'd be willing to bet he'd be an even bigger asshole during an appointment  
Sounds like the kind of guy who will try to bargain or steal his donation back or any of the usual crap bad clients try to pull off.

Do us all the favor and post his details in provider onl