Please follow the below procedure to change the Picture Size on the Television.
Step 1:- Press the Menu key on your TV remote, scroll down and select Function
Step 2:- Scroll down to the Option Aspect Ratio to change the picture size. Select Aspect Ratio Setting to 16:9 and the desired presets such as Movie/Subtitle/Native Panaroma
NOTE: If the Aspect settings on the TV is unable to change the Screen Size then Please contact your Cable Service provider to change the settings