A lesson in persistence. I got hit with a schedule change this past Saturday, 12/2. The flight was DL317 from HNL to JFK on 1/13/24 on a B764. I was in seat 31C (Comfort+ aisle) because I have complimentary upgrade via Platinum Medallion. It's a 10 hour redeye, so I wanted aisle for both access and just a little more room. Delta cancelled and rebooked me on DL312, same travel dates, same aircraft type. Now I'm in 32D (Comfort+ Middle, center section). And I cannot change seats, even back to Main. Everything is either occupied or unavailable. Being Schedule Change Saturday, I gave it a couple days to let the kinks in the system work themselves out. Nothing changes.

So I call Delta Reservations (first call): "No seats are available". I know this is not true, but maybe it just needs more time.

Next day, call Delta Reservations (second call), I ask about paid upgrades thinking maybe if I offer money that might change things. Nope.

I do a dummy booking of the flight while not logged in and there are plenty of available seats in all cabins (except Comfort+).

I email Delta Customer Care, am told that since flight is in a couple weeks out, I should call Reservations. Literally no help whatsoever.

Now Thursday, Call Reservations (third call), ask why I cannot change to *any* seat. I ask about upgrades and am quoted $2K for all my flights that day (not just the HNL-JFK segment I'm referring to). Ask to be moved to Main. Am moved to Main Cabin and all of a sudden there are plenty of available seats and upgrades available. According to the agent, the issue was apparently my Complimentary Upgrade for being Platinum. Not sure I buy that, but the results speak for themselves. So, don't give up trying, it may take a few calls until you get a good agent that will actually help.