Some (many ?) people on FT prefer to make changes to xONEx or xCIRCxx tickets through the selling airline.
...
My current DONE5 was issued by BA (first flight was CPT-JNB on BA in January)
So far (already), I have made two changes to the itinerary (neither involved changes to Ticketed Points)
And both were quite painless - apart from being put on hold for ~15mins each time, while the agent verified that no change fee was payable