For advanced bookings, touch the girl emoticon at the bottom right screen of your app. From here, click “Upcoming Trips” and touch the trip you wish to cancel. Swipe the trip from the right to the left side of the screen and a little red “cancel” button will appear! You will not be charged so long as you cancel over an hour before the scheduled trip.
For instant bookings, the cancel button is in the lower right corner of the screen. Once you touch it, you will be asked if you are sure you want to cancel the ride. If the answer is yes, slide the green arrow to the right. You will not be charged as long as you cancel before the 5 minute mark of booking the trip!