Certainly, both learners and instructors have the ability to reschedule or cancel a session up until the permitted timeframe established by the Admin. To modify a session's schedule:

Log into the account and navigate to "Sessions".
Find the intended lesson listed under "Sessions".
Select the "Reschedule Session" option for the session in question.
In the dialog box that appears, provide a reason for the rescheduling to inform the student, then click "Send".