Why is my iPhone acting up?

[mhmmm.]

I just got the new 3G iphone (32 GB) , and a couple days ago this note saying, "This accessory is not made to work with iPhone" and i have no idea what its talking about! I did not put ANY "accessory" in it! Also, the volume has stopped working completely. Also, when i'm on the phone the screen turns black and doesn't respond to my touch! WHATS HAPPENING?! It is broken? HAVE ANY OF YOU GUYS EXPERIENCED THIS?! WHAT DO I DO? please help!! thank you so much, merci beaucoup! xox