Yes, it is possible to cancel or reschedule a class of a course.
1. Go to Settings>Classes, courses and events
2. Click on the course
3. Go to the Schedule tab
4. Click on the specific course where you want to cancel or reschedule a class
5. A pop up window will open showing the classes of the course and their dates. Click on the class you want to cancel or reschedule
6. Click on the Delete button to cancel the class, or change the date and time of the class to reschedule it