Originally Posted by SamOF

You can't waitlist a KL flight anyway, so that's just a terrible agent.

FWIW, my go to phrase is not to ask to double check the correct inventory, but to actually say (as sweetly as humanly possible) "And just to check, you're looking at Z class on the KLM flight numbers, right? Not for OY?" It's a little aggressive, but the problem is usually that they think they are looking at the correct inventory, so the answer to your question will always be yes.