Yes, a learner/tutor can reschedule/unschedule a lesson till allowed duration (24 hours). To reschedule a lesson:

Sign in to the account. Go to "Lessons".
The scheduled lesson will be listed under the "Manage Lessons".
Click on the "Reschedule Lesson" icon of the lesson.
A pop-up box will open. Mention a comment for rescheduling the lesson for the learner/tutor and click "Submit".