If the screen doesn't rotate when you turn it sideways, first make sure that the 
Auto-rotate screen option is selected in 
  (or Display, gestures & buttons). 
If 
  Auto-rotate screen is already selected, try recalibrating the screen if the screen orientation doesn't respond properly to the way you hold your phone. 
 
 - From the 
				Home screen, tap 
				 or 
				Display, gestures & buttons. 
			 
-  
Tap 
  G-Sensor calibration. 
-  
Place the phone on a flat and level surface, and then tap 
  Calibrate. 
-  
After the recalibration process, tap 
  OK.