Why does this message keep appearing on my screen to enable blocking mode enable at least 1 function?

[AC Question]

this message keeps appearing on my screen to enable blocking mode enable at least 1 function

I have a Samsung galaxy 4. the above message keeps appearing on my screen when im using the phone.This shuts down the call and if I press [ cancel or ok] it wont work.I have to turn of the phone and start again to remove it from the screen .what should I do to stop this