The term usher certainly is used to refer to someone who checks tickets. I enjoyed this example from the BNC: Then the skinny fey usher in white gloves neatly snips your proffered ticket in two: with a pair of nail scissors. But are you looking for a word to use to distinguish between those who look at tickets and those who show you to your seat, or something else?
Here, an usher is someone who shows you to a seat. We don't have ushers in our movie theaters (cinemas); you find a seat by yourself. There is a person at the door who takes your ticket, tears it (no scissors), and hands you a stub; that person is a ticket-taker.