I've got two seats booked in World Traveller Plus on BA1529 Miami to LHR on the 8th January 2024. The flight is operated by AA, but booked with BA. It's a return of a round-trip.

The original flight time has been pushed back by two hours and five minutes. I, ideally, would like to be rebooked on BA0206 (BA metal) which is closer to my original flight time.

Spoke with BA today and believe two hours is the magic amount of change to be allowed to change flights without fee. But while I can see availability for the BA0206 online, and with a dummy booking even select seats, the agent tells me they can't see any availability / no seats available to move us to.

Looking more closely, it's not possible to book Premium Economy round trip on that flight, but is as a one way flight.

Any tips or ideas on what the issue could be? I know it's often worth calling back and trying another agent, but trying to think in advance about any argument, explanation, or detail that makes moving to the earlier flight more likely.

Welcome any advice or suggestion.