Post Consumer Brands’ Honey Bunches of Oats is naming San Francisco-based Argonaut as creative and social AOR following a competitive review held internally by PCB.  The Minneapolis-based Public Works served as AOR for only a year.  Honey Bunches of Oats will have to undergo a significant brand overhaul since its long time spokesperson Diana Hunter (who actually worked in a Post factory where the cereal was made) announced her retirement last year.  The company employee turned campaign star first appeared in a commercial for the Post cereal brand in 2015 when she was shown speaking …