This.
There is no reason to call AA yet again. If AA is going to charge you, you have a decision to make as to whether you pay & fly or make some other arrangements. If it is not, you are all set.
How will it change your actions if AA tells you that the first agent made a mistake and should have told you there is an add/collect due at the counter? Likely it won't. No reason to stir the pot by calling yet again.