Ringer/Silent button is backwards.

I used to have an iPhone 3GS and I got the 4S for my birthday which is in January. I never really noticed this until I was using my sister's iPhone 4. But my ringer/silent switch is backwards.... On hers, you push it towards the front of the phone for the ringer to be activated (it also vibrates). And when it push it back, it goes into silent mode. Mine is the opposite. When mine is pushed forward toward the screen, it goes to silent mode and vibrates. When pushed back, it goes to ringer....

Is anyone else's phone have this?