the light on my screen doesn't turn off please help?

If you mean the phone doesn't auto-lock and go to sleep:

Settings > General > Auto-Lock > choose the time limit you want (shorter saves battery)

You know that you can manually lock and shut off the screen by pressing the on/off button on top of the phone at any time, right?

I have this same problem on my iPod Touch. I held off for as long as possible to get the use date and accidentally let it update recently and my screen won’t turn off automatically like it used to. #boycottupdates

Try Settings > General > Auto Lock > 1 Minute.

If that did'nt helped, do a reset (Hold Sleep/Wake and Home buttons about 10 secs or more till Apple logo appears)

If Phone lock than light don't off and always on light the screen and also charge to low and switch off phone