The smartphone is used to access in-game information such as relationship stats and more (besides calls and text messages).
You can access the smartphone on the event choice screen and in free roam events, providing it’s not lost, stolen or left behind (like in a locker).
Once you have someone’s number you can call or message them if events are available. You can also customize their name and profile picture (displayed on the phone only).
You can also change the background picture to any image in your smartphone’s photo app.
Other characters may have access to your phone, for instance if they asked to borrow it, or if they’ve found it somewhere. Your choice of profile picture and background picture can have an effect on your affinity when someone looks at your phone. A girl might not like finding you’ve used a picture of her mother as your smartphone background, or if she believes she is your girlfriend she won’t appreciate a picture of another girl.