Originally Posted by VrefPlus5

Hey travel gurus

Used my travel bennies for the first time recently, didn't really go as expected. Maybe I'm not understanding this quite right....
I traveled with my dad(D2 passes) on 2 American flights operated by Compass airlines. While booking, I chose first class for both of us as there were enough seats still available. I checked in right on the dot 24 hours before departure.
Now, I know I'm not entitled to anything and it's all based on availability but-
Both times when I checked in at the gate, we were denied first class seats, on the second flight the agent straight out told me they don't give first class seats to standby passengers. Then she said they didn't have first class seats available even though the priority list still showed 3 seats available. Then they gave a first class seat to someone below us on the list(D2R if I remember correctly, not sure if that's a higher or lower than D2).
Here's the odd part- Both times there were a couple first class seats left vacant after boarding was complete. I understand paying passengers get priority but this didn't make any sense to me, we couldn't get the seats we had booked under even when they were available.
I didn't want to argue with the agents so I just let it go.
Am I missing something here? The priority verification card we get on Check In doesn't say class of service requested and the agents didn't seem to have any idea about the requested class in their system.
How can I make sure we can get these seats when they are available?
Is there something I can tell the agents to refer to(without sounding rude, of course) if they don't understand the process?

Appreciate your input in helping me use my benefits to the max!