You may cancel your appointment without incurring a fee until the professional has indicated that they are on their way to the job. You will get a notification that says 'En route'. If you cancel after the professional has indicated that they are on their way to the job, you will be charged the minimum fee.
If the professional does not arrive at the premises of the job within a reasonable amount of time after the expiry of the appointment window, your cancellation fee will be waived.