You can cancel a booking at any given time.
Login to your profile on CarAmigo and visit the section "My Bookings". Find the booking you want to cancel and click the button "Cancel the booking".
Do take into consideration that for canceling a paid booking 24 hours before the actual start of the carsharing you will be penalized and will receive a publicly available negative note on your profile. If you're a car owner we strongly recommend you update your car calendar regularly, in order to avoid negative notes.