TIL about oldest known written complaint from a customer named Nanni who received the wrong grade of copper from merchant named Ea-nāṣir. It's estimated at being over 3,800 years old (~ 1750 BC).
https://en.wikipedia.org/wiki/Complaint_tablet_to_Ea-n%C4%81%E1%B9%A3ir#cite_note-1
