It is like they have two different systems when you call the agent. The agent looks up the flights availability and quotes the price difference and any service fee from whatever screen they are on for this. Then when they go to complete the purchase to reisue the ticket, they get a very high quote. They seem to realize that this quote is too high and so they come back and say they have to do the reticketing off-line.

When you use the app/web to do the change, you only get the high quote and nothing you can do with it than just pay whatever it comes up with. The change fare in the app, in my case, varied from $1200 to $4700 for PE for changing return flight dates. The agent quote was less than $400.