Explained a situation at a bar I'd worked at - always being polite, keeping calm, not getting angry and genuinely trying to offer help to solve the person's problem. Sometimes people just want to throw a bit of a paddy and there's nothing you can do about it except be polite and helpful until they calm down and are pleasantly surprised at your lack of confrontation. If they're just getting furious, playing the old 'I'll get the manager' might appease some of those Karen's out there you know.