We require an available 20 business hours to work within a given week to qualify for the fixed rate plans.  It is tough for us to book appointments only within limited time windows, as we are working to coordinate at least two people’s schedules.  Usually, and ideally we will coordinate with a Google Calendar to have the most possible options available.  If we are just filling a designate block of time, If something comes up within those allotted times, please notify us right away so that we can block out that particular time.   If we are not notified ahead of time, the onus of rescheduling the appointment becomes yours.