But if you check on your reservation and there's a change more significant than the app and site can let you handle on your own--it seems to me like slight time changes are fine, but not when flight numbers change too--you have no way of knowing if it's a ten-minute change or a more significant issue unless you either 1) call in and get it fixed or 2) try to recreate your itinerary on the AS site or Google Flights and figure out how big the change is... in the time it would've taken to just call.