Instructions
Wait until the cutscenes end and you have full control of your character on the street. Press the up arrow on the directional pad two times and your character will pull his cellular phone out of his pocket. A number pad icon will also appear on the bottom right corner of the screen.
Enter any number you wish by using the directional pad on your controller. There are various codes to enter and contacts you can call throughout the game.
If you hear a ringing sound while you are walking on the street, press up twice on the keypad and you will answer a call. You will get these calls periodically throughout the game.