Correct. No seat selection for free unless you book a flex fare or above. Exception is if you are traveling with a minor (12 or under, I think...maybe its 14) where they will basically put you in seats together, but don't let you pick which seats (not necessarily all - 1 adult with the minor, you have to call, or it will be done automatically a few days before the flight). My experience is that by default, they put you way at the back of the plane, even when there are lots of empty seats everywhere else, and YMMV on calling to be asked to be moved up in advance - I've had occasional requests honored, but also had them refused.