As quoted from the "Fare Rules" on Cebu Pacific's webpage:
YEAR-ROUND FARES
Flight changes must be made more than 4hrs before date of departure with the following options: (1) rebook the flight subject to applicable fees and penalties, (2) cancel and store it in a Travel Fund subject to penalties which may be used within 90 days, or (3) transfer the booking to another person for a fee.
Lite Throughfare must be used in sequence, as booked. Flight changes or cancellations are not permitted once any of the segments has been used. There is a nominal fee included in the Lite Throughfare.
PROMO FARES
Promo fare, Lite fare with promo discount and its applicable fees, taxes and surcharges are non-reroutable, non-refundable and may not be stored in a Travel Fund but are rebookable subject to applicable fees and fare differences. Rebooking must be done more than 4hrs before date of departure. These are not rebookable to another promo seat after the sale period. Please refer to Fees Summary for certain exemptions.