If there's a specific client you'd like to block from booking with you online, you'll be able to do that with these quick steps:
Click the three lines in the top left, and choose Clients from the menu
Head into the client's profile page
Scroll down to "Client Scheduling Settings" section of their profile
Select "This client can never book online." from the options, and save!
This will disable their ability to book you online in the Schedulicity Marketplace and will instead display a message that they will need to call to book.
👉 One thing you'll want to keep in mind here, is that in order for a client to remain blocked from booking online, their client record needs to remain on your client list. Just make sure to not delete a client after you've blocked them from booking online!