How to cancel a Genius Bar apt

If you have iOS though, you can cancel or reschedule using Apple's Apple Store.app. It's not obvious how—

From iOS online Genius Bar appointment:

https://itunes.apple.com/us/app/apple-support/id1130498044?mt=8

1. Tap Stores
2. Find store where you have reservation.
3. Click Store then Genius Bar. From here you can create a new appointment, or cancel or reschedule an existing appointment.

Another idea: if you have the email confirmation, there should be a link which will let you cancel it.

Call the store.