In case a ride was booked incorrectly it can be canceled. There are only two ways a trip can be canceled: through the Passenger app or the Command Center. Shuttle Drivers can't cancel rides; they can just finish/complete a ride.
On the Passenger App
If the ride is scheduled, the Passenger can cancel the ride on the app. The "Cancel Ride" button is not the exit button for the app, once pressed/clicked it will cancel the ride booked.
On the Command Center
If you wish to cancel the ride, go to the ride flyout. Just scroll to the very end of the ride request and the Cancel option will be there.