係（かかり） means the person in charge of a specific task or duty.
It is often used as a suffix after another word. In that position, the reading commonly becomes 〜係（がかり）, as in 受付係（うけつけがかり） for “receptionist” and 案内係（あんないがかり） for “guide / information staff.”
Used by itself, 係（かかり） refers to the person handling a particular matter, such as the staff member responsible for your case or request.
Important: 係 is about operational responsibility, not rank. It means “the person assigned to this,” not necessarily a manager or supervisor.