The Bookit plugin allows creating free services. It is enough to simply leave the service price at zero (0) by creating or editing the service.
Afterward, created service can be attached to the staff.
The customers can book the available free services.
The payment method will not be displayed if the service is free.
Also, the client will receive the confirmation email without fields connected with the payment even if they exist in the email template.
As you can see, the fields [payment_method], [payment_status], and [total] automatically ignored since this service is free.
On the dashboard, the payment status will be automatically changed to complete.