Originally Posted by SamOF

Aha. This suggests that the GA for your new flight cleared the UG list too early—hence the agent had space to book you into J but there were no seats. As someone who sometimes check in late (but legally so) for flights, this always annoys me, and I think is worth a complaint in and of itself.

Once, I had to book a very last minute ticket, and I bought an A fare. This was T-50 or so. The GA had already cleared the upgrade list, so tried to give me a Y seat. I wasn't happy.