my I phone 4s has gone into locked screen mode it how can I rectify this please help

all i get is my normal screensaver screen with a box around the time and a mans voice stating the time and locked screen. I have tried turning it off and then on again but problem still persists

I suggest trying a soft reset :

1. hold both the home button and the lock button until the phone resets.

If that doesnt work you may have to do a hard reset (Warning: this will clear all your contents and settings!!!!!):

Go to Settings.
Tap General.
Scroll to the very bottom and tap Reset.
Tap Erase All Content and Settings.
Tap Erase iPhone. iTunes (download it here) will then begin restoring the phone to its original factory state.
After the process is complete, your iPhone will restart and you’ll be presented with the “Slide to set up” welcome screen, just like when you turned on your iPhone for the first time.