What do you call a person who says one thing and does another?

A person who says one thing and does another can be referred to as a hypocrite. Hypocrisy is the practice of claiming to have moral standards or beliefs to which one's own behavior does not adhere. It can also refer to a person who feigns some desirable or publicly approved attitude, while actually engaging in contrary behavior. Hypocrisy is often used as a form of deception in which a person conceals their true intentions or character. Hypocrisy can be seen in people who make a show of being moral or righteous, but then act in a completely different way when no one is looking. It can also be seen in people who claim to have strong beliefs, but then act contrary to those beliefs when it suits them. Hypocrisy can be damaging to relationships, as people may feel betrayed or deceived by a person's words and actions.