They're automatically picked up after 3 rings of the phone.
In night 1-5 and night 7 you'll get your phone calls.
Night 1-3 where the other security guard drills you to the game.
Night 4 where night guard is getting fumped by Freddy.
Night 5 where night guard gets his uhh... (Gonna skip this part)
Night 7 an unknown dude asks you about your days of work then leaves