To stop a Participant from posting in your Chat Room, you can use the option to "Suspend" the Participant.
To suspend a Participant, simply go to your Dashboard, and under Chat Room find the Participant you want to suspend and toggle the "Suspend" toggle to suspend them.
When a Participant is Suspended, they can still access your Chat Room, but they will no longer be able to post a message. The suspended Participant will see a message that says, "your chat privileges are currently on hold".
To re-enable a Participant, simply toggle off the "Suspend" option for that Participant.