You can find this trophy by opening the door that has "Comm" on it in Shi No Numa. Then, open the door where the perk machine is located. There is a door on each side of the perk machine. Go in the one on the right. As soon as you enter that door, take a left. There is a black phone sitting on the table next to a radio. Go to the phone and hold [Reload]. You may need to do this two or three times. You will start to hear numbers being dialed, it will start to ring, and the trophy will be unlocked.