Why does my call is on speakerwhile dialing or receiving a call even if don't put it on speaker?

[AC Question]

I bought lenovo vibe k4 note in September 2016. Now a days it automatically puts my call on speaker while I dial or receive a call, but this happens sometimes only I have to press speaker button twice to switch to earpiece mode.
Plz help..

 

[n apple]

You should try settings > apps > all apps / system apps > look for phone: and clear cache (and data if needed) then force stop it, go back to home and go to the phone app