This usually happens when your phone update has been stopped. So that you cannot receive any update. So you use your mobile without any update. But if you want update, then, you can download from Sam mobile of its update and install in your mobile and you view from youtube how to install it.
I also face this problem, but i recommend you don't do it because i can't do any risk. But if you want, then, go phone market and learn method and then you install it personally