Last week of my internship or so I though? How to handle this?

[turnipmonster]

ask your boss if he has a minute to talk about something (i.e., don't talk to him about it in the hallway or by the coffee pot or something). explain to him that there was a misunderstanding and you thought you'd have that week off, and thus made plans to (go away with gf/road trip with friends/donk off all your money playing tourneys). whatever.

tell him you can probably get out of the plans you've made because you don't want to leave on bad terms of course, but is there any way he can give you the week off? basically you want to come across as being nice and willing to go the extra mile for him, but at the same time make him feel like a total tool for not giving you a week off. throw something in about it being your senior year to give him some perspective.