Red Phone 1 - This phone is found at the bottom floor of the spawn room and it is next to the white number on the wall right next to the fire hydrant. You have to interact with it.
Red phone 2 - This found directly to the right of Widow's wine. you have to interact with it.
Red Phone 3 - Found in the room where Mule Kick is and its under the tv where the box would show. Now you can interact with it.