Star Alliance - RTW: change of routing after 1st international segment flown

If I recall, there is a $125 (or $150) change fee plus whatever taxes, but no other add/ collect, right?

I just had a RTW reissued. Travel has already begun. UA seems to have recalculated the fare to the current rate rather than the rate when I first ticketed it.

Seems UA made a mistake. Never had the fare change (unless i go to the next mileage level up, and even then it is calculated based on the old prices)