Do you have to be online to use the phone in Grand Theft Auto iv?

Answer 1

Throughout the time I have played GTA IV on a games disk, and not on-line, I have been able to use Niko's cellphone OK. I have not tried to enter any cheat codes though.

This may be something you already know, but, just in case, I am copying some of the notes on the phone use for you, in case it is of help:

To use Niko's phone on GTA IV (for the PS3):

To activate phone: press upwards once on the directional pad. To access friends and saved numbers press "x" for Phonebook, and also for Options etc.

To dial a number, e.g. 911, cheat codes, etc., activate phone by pressing directional pad upwards twice, showing blank screen ready for number input. Choose numbers required by using directional pad, pressing "x" on chosen number. When all numbers on screen, press the telephone icon on the left hand side and number should ring.