That's how most (if not all) banks work in France. They charge you overdraft fees as a loan at the maximum legal rate (which is about 20% annually, or 1.5% mont

That's how most (if not all) banks work in France. They charge you overdraft fees as a loan at the maximum legal rate (which is about 20% annually, or 1.5% monthly according to Wolfram). That way, if you have a 2 € overdraft for one month, you'd only pay 3 cents of fees. However, if you have 1000 € of overdraft during one year, you'd pay a total premium of 200 €. Seems to make much more sense than a flat fee.