Great detective work. Yea from their FAQ seems you can’t amend or cancel until after the first six months. Hmm I wonder why. Vampire addicts I tell ya.

Auto-ship is a privilege granted to customer committed to their quality of life. It comes with substantial savings. This privilege should not be abused for the mere sake of a one-time saving. In this regards customers cannot suspend their auto-ship privilege before six consecutive months. Within this period they can upgrade at any time. After the six month period they can cancel, amend or suspend the original auto-ship understanding. Thank you for your understanding.