Originally Posted by
Stranger
Alas, concierge office is closed until tomorrow morning...
And on line check in did not even offer the option of same day change, even though my ticket says it can be done for $75 each.
The option only shows if there is positive space on the flights you're looking to SDC to. If a given flight as a whole is oversold by even 1, the option to SDC to that flight will not show (remembering the caveat that only the next two available flights will be presented).
Given the long weekend, I would suspect that the flight you're attempting to change to is oversold.