Charged for what? It just does a new payment for the new phone this month, and for me (going from Xs Max to 11 Pro Max), it's the same cost. No change at all.
You don't need to do anything. The phone will be mailed to you, and you will get a box to send back the old one. It's completely painless now (finally). Just follow the documentation at MR on how to backup/move data/wipe out your old phone.