Default OnePlus One volume buttons problem

Hey, I've got recently a Oneplus One but, when I turned it on, I found that he has a problem with the volume buttons, I mean when pressing for example the vol + button it will not turn it higher or what, same when pressing the vol - button . I also found that if I take pressed the vol + or - buttons it will change from normal to vibration, just that. It seems like they are blocked or something, I don't know :\ Can someone help me understand what I can do with it? Sorry for bad english!

Ps. I'm italian, lol