售票大厅 is one of the many possible ways to indicate a ticket office. The word 大厅 in 售票大厅 literally means big lobby. We have seen different words used after 售票 for ticket office, which incolude 处 (chu4, place), 亭 (ting2, pavilion) and 厅 (ting1, lobby/hall). Which word to use after 售票 depends on the physical size of ticket office, which is not yet standardized yet. But anyway the key word here is 售票.