When I've tried this at the airport, it's a 50/50 proposition that an agent knows how to do this. Thus, I'm trying to take care of this ahead of time.

Ideally, I'd like to avoid the situation you had when you called in, the person said it was all set, but you found out at the airport that it wasn't.

Is there anything specific I should say when calling in to make sure that this is completed correctly?