Let them leave negative feedback: screencap their texts. Register for an account, submit it as reply in the thread or to the mod. Problem solved.
Further option:
Then go to the Police, show then that they acted on this and that they tried to force you into having sex with them via coercion or to give them money (the fact that you are a sex worker makes no difference, it is sex via coercion aka sexual assault, threatening you as you won't give them sex or money in lieu is blackmail and harassment) them via blackmail and and threats demanding money, there is most likely a Police officer that is willing to give them a call (try to approach a female officer where possible) and tell them a report has been lodged and they will be investigated and charged for harassment if it happens again.
Consequence of this option:
It's a burner phone, not registered to him. This prompts further shitty behaviour and he makes your life hell. Might be easier just to call his bluff, go for option A if he does do anything and prove that it is a fake review since you have evidence of someone threatening it..
Block him, ignore him, google search your name regularly and search the review forums.