Phone Guy is somewhat nonchalant, and there is absolutely no explanation as to why. Throughout the game, he does his best to inform the player that there's "really nothing to worry about," despite the obvious danger. It's unknown if he's lying to the guards out of free will, if he's obligated to do so, or just trying to make Mike Schmidt feel better.
He seems to be very hesitant and awkward at times, often stuttering and nervously laughing, implying that he might be worried about the possibility of someone hearing his warnings and advice regarding the animatronics. Of course, it's also likely that he is generally anxious and on edge because of the imminent chance of death at their hands.
Phone Guy is the previous security guard at Freddy Fazbear's Pizza, who worked in The Office during the week prior to the events of the game. He helps the player by telling them about the behaviors of the animatronics at the start of each night until Night 4, which is his final message.
Players dispute whether or not the Phone Guy is actually an ally, saying it seems odd that he insists that they stay, and downplays the situation instead of telling them to quit or leave immediately. While he may be a forced ally, he's the only one the player has. [Source: wikia]
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