Hi - we had a flight change notification on return flight BOS-DFW including an aircraft change from 321 to 757. I called to try to change to a different flight same day on 321 but was told since time change was less than 2 hours we'd have to pay fare difference plus change fee x2 = $500. Agent said aircraft change does not qualify. Is this correct. The aa.com website does not show wifi or power on the flight that is now a 757 and while less than 2 hours it will get us in later in the day than we expected. Do we have any options? Thanks.