French phrase
Vous m'avez facturé ~ de trop.
Meaning
You charged me ___ too much.
When to use it
States that an excess amount was charged. It is fairly direct but still calm, often used to request a correction.
Example dialogue
Vous m'avez facturé 20 euros de trop.
You charged me 20 euros too much.
Je suis désolé, je vérifie la facture tout de suite.
I'm sorry, I'll check the bill right away.