Use the mobile app.

And yes if you cancel a points reservation and are not PC, you might lose some of your points:

If a reservation which was booked with points is cancelled within 24 hours of booking, all points will be returned to the members account. If a reservation which was booked using points is cancelled more than 24 hours before the pickup time the following points will be forfeited: If a Gold member, 50% of the points used toward the booking will be forfeited; If a Five Star member, 25% of the points used toward the booking will be forfeited; If a President’s Circle member, all points will be returned to the members account. If the customer does not cancel the reservation prior to the time of pick-up and the rental vehicle is not picked up on the rental date, all the points used toward the rental amount will be forfeited, regardless of the members tier status.