The only way to "carry" a cell phone is to use the Randomizer to completely alter your character to one that has the cell phone. It cannot be added, picked up, or costumized. There is a cell phone on Nabooti Island but it is never held.
NOTE
Randomizer settings : CTRL + Shift +R are notreversible!
When you have your cell phone call: 555 6789
no
At the bottom of the cave.
The phone number is on the shovel they gave you.
411, 511
you dont
5556789
you call the number from the shovel
I think it is possible to hold a cell phone while driving!
5556789
you cant
you have to go in the subway and above the train get the cell phone