If at all possible, avoid cancelling anything, if you make a booking, try and change it over cancelling it.
I have made no less than a dozen changes to KUPP bookings in the past 12 months (A & P fare buckets)
All were either change of dates (same flight sectors) or same date but re-routing.
No charges or fees have ever been applied
An example of such, my most common sectors in the US are LAX>DFW>CMH (a good little earner btw, especially when it was closer to $600 (now approx $700)) I would bring them forward or push back a day.. no problem
Or, due to time restrictions, I may have booked CMH>ORD>LAX and due to a higher then normal risk of bad weather (mainly in Winter) I would change the routing from ORD to DFW… again, no charges (obviously I check online first to ensure fare buckets are still available).
I have asked about cancelling a sector all together, and was told there would be charges/fees applied… when that happened, I just used it as a MR and flew back on a dirt cheap Q fare and booked the flights I wanted a few days later
I am not sure if status (Emerald) helps with this, or I have just been lucky