The appointment can be cancelled from the mobile phones or the website.
Website
In the Calendar Page click on any appointment that is purple in color. On clicking a new dialog box will open where you can click on the Cancel Appointment button to cancel the appointment.
Android
In the appointment listing swipe the appointment card to left. Click on the Trash can icon to delete the appointment.
iOS
To cancel an appointment swipe left on a appointment listing to reveal the cancel button. Tap on the cancel button to the cancel the appointment.