CX doesn't have change fees on quite a lot of lower fares, but exactly which subclass varies by route. For example, I am currently in MNL on an M class HKG-MNL-HKG ticket (which is actually the cheapest published fare, being a Diamond). There is no fee for a change of date/time provided that you do it before the date you were originally due to depart, but there is a "no show" fee of HK$300.
In general the subclasses go YBHKLMV in that descending order. Tickets aren't readily available in all subclasses on all routes.