My bad. I thought he said the fee was for outside of 21 days, not within them.
Dan's correct that no fee is applied if it's outside of 21 days.
not sure why you changed your mind.
Here is the official united policy
Changing the cabin, award type, or changing a flight to a different airline, regardless of departure date(3) $75
This is pretty clear 75 dollars
Regardless of departure date so if you change airlines like I pointed out from Turkish airlines to United within or outside 21 days you get charged. Now if Dan is saying that can be waived if you call then that is something else. Can someone confirm that is what Dan means but not sure why you backed down from the official United policy