When you reactivate an account you get the character choices.
When you upgrade, you do not. That's what you did here. First time was a reactivation, the second (going to premium) was an upgrade.
What you can do is email feedback, or billing (I'd say feedback). In the email, put your account name, and you can either ask for a list of characters, or tell them which you'd like made active. You can also call them, but I find it easier to do via email given how...odd character names get.
Email verb in game if you don't know them. As in, type email, then hit enter.
