Banks generally calculate it with a fixed daily fee for each day you're overdrawn plus interest on the amount over the limit, and Société Générale applies its own rates that can be pretty aggressive. After 3 days on 150€, it's no wonder the bill stings, especially since the fees pile up fast. You can absolutely call your bank and ask for a reduction, especially if it's your first time or you've got a good history with them - advisors often have some wiggle room to negotiate, you just gotta be nice about it and explain your situation. Otherwise, you can also compare with other banks that charge lower fees and threaten to switch accounts, sometimes that pushes the advisor to be more flexible.