These rideshare apps usually have you schedule for ASAP rather than for some future time, so chances are if you cancel it would be much sooner.
Not sure about this company, but for Uber the cancellation fee should only happen if you cancel after five minutes of scheduling a ride. I've seen Lyft and other rideshare companies have similar policies.
http://support.uber.com/entries/22326831-Ride-Cancellations