The feature is by default in your facebook . when you open your facebook account so the message or call notification is show on the main page. if you want to close the notification so you can close the notification of chat tabs or call tab bye turning off .
In fist step open your facebook account and go to setting option.
In second step if you want to turn off chat tab so select the turn off chat tab.
And if you want to turn off call tab so select the turn off video voice call option.
In this step message box will appear so select one of them and click on disable option.