You are able to cancel your appointment from the TM3 Online Booking Portal.
Login to the booking website or register a new account using the 'Login / Register' button. Once registered or logged in click on the 'My Bookings' tab.
This will show you a list of your booked, cancelled and previous appointments. Click the 'Cancel Appointment' button on the appointment you wish to cancel.
You will be asked to confirm your cancellation. Click on 'Yes.'
The appointment will now show as cancelled within the My Bookings page.