If there is a secret in the GTA 5 game, you can bet that the players will found out about it, even if it took them more than a year to find it.
The players of the game GTA 5 might have stumble across a secret in the game that requires the player to call a random phone number on their cell phone. The secret was discovered by a player that goes by the name Karma Ingram on Twitter who posted on his twitter page that players will be able to trigger an explosion and change the appearance of the phone in the game if they call the number 1-999-367-3767.
Kotaku, who came across the posted tested out the number proving that the number works. The question now is where the number came from and if the number is connected to any other thing in the game.
Nobody knows if the number was there since the game was released back in 2013 was whether it was added later but if you own the game, you might want to check it out as well.