In terms of changes, I think it’s easiest to think about it this way: changes are free and unlimited so long as you keep the same individual segments, stay within the parameters of the fare rules (min, max stays, advance purchase, and the booking inventory, such as E). As such, CX is essentially just revalidating the existing segments to be new days/flights. Any other changes to the ticket may cause a change in the fare (you’d pay the difference between the fare you paid and the new fare), BUT you won’t have to pay the additional fixed “change fee”, such as USD100. If a pax wants to do a reroute (for example, new origin, destination, connecting points, etc, then the pax might need to pay the difference in fares (if the new ticket is higher priced), but won’t need to pay the fixed additional service fee (Ie, reroute fee).