Originally Posted by
xliioper
To be clear, the fare difference must be greater than change fee to get any credit back. If the new fare is $150 less and the change fee is $200, you will still have to pay $50.
That's not how it works (anymore).
You have to pay the $200 in new money. You then get $150 back in credit to be used within 1 year of initial ticketing. Exceptions vary if the fare is "refundable" (ie, to cash), in which case you can do what you indicate. Those fares tend to be more expensive, however, and not in the leftmost column of fare choices..