The phone calls indicate the Safe Room is sealed before Phone Guy dies, however FNaF 3 minigames are implied to occur after FNaF 1, after Phone Guy died.

Eventually, thirty years after the Pizzeria shut down, the Safe Room was found by the Fazbear's Fright crew, who retrieved Springtrap from the room, after which it is unknown if it was resealed or left open. William eventually ran towards the Spring Bonnie suit in the room, putting it on and hoping it would protect him, however the suit had a springlock failure, and William was left to die in the suit in the Safe Room. However, in doing so, the souls within the animatronics were released and barred the entrance of the Safe Room, while a fifth Soul chased the terrified William around the room. William Afton, hiding in the Safe Room, used this to his advantage, and dismantled them one by one. In the FNaF 3 Minigames, Shadow Freddy lured Freddy, Bonnie, Chica and Foxy up to the Safe Room, which they are unable to enter. According to the map of the minigames in between nights in the third game, this room is right next to the Restrooms, near the entrance.

This room ended up being covered with a false wall, Fazbear entertainment claimed this was due to budget restrictions. According to both the phone calls and minigames in Five Nights at Freddy's 3, there was a 'Safe Room' that was hidden from the cameras and was invisible to animatronics, where employees could put on the Springlock suits, and bleed out in if necessary. The Safe Room is a secret room within Freddy Fazbear's Pizza.

Is mine imator safe