Originally Posted by
pvitoria
Yet I went to the continental stand at the airport and they told me that after the flight started (I assume after I check in for departure) I can change the return date, subject to a fee of 250$ and availability of seats. Can anyone confirm this, or does anyone ever tried it?
No, the CO Agent informed you incorrectly, or you mixed the two options.
At check-in (24 hours before your flight) you can change your flight to another one that is within (+/-) 12 hours of your original departure. That option will cost you $50, assuming you're not a Platinum or Gold Elite.
The $250 only comes in if you are changing your return date beyond the timeframe above, and you can do this anytime.