If you offer online booking, your users can generally book any staff members available for the selected services online. If you want certain customers to not have full selection, you can configure this in the respective customer accounts.
Prerequisites for blocking specific staff members
- You allow online booking only with login.
- Your customers must log in before they see the available staff members and free appointments.
1. Check online booking mode:
Under Settings > Online Booking the option "Registration mode / Allow booking appointments without login" must be disabled:

2. Check registration mode
Under Settings > Online Booking > Basic Settings > Registration the option "Also show available times, then prompt to login" must be disabled:

Set up a block for a team member
To prevent a customer from selecting one or more staff members in online booking, open the customer account and open the block dialog:

You can then select the desired person who should no longer be bookable by the customer in the future. A reason is not mandatory but can provide transparency. It is not visible to the customer.

This way, the customer will no longer see the blocked staff member as an option in online booking.