I'd be concerned. Might try calling again, to see if the situation has changed.

You might have been FAM'd and they may have few options. We have no right to a specific seat, so a polite request, rather than a demand, is the most likely path to your original seat...

Show up early, ask at check-in, ask at the lounge, ask at the gate... might be a good time to investigate a bump, at least you'd get compensated for losing your original seat assignment.

Hope something works.