oh you're in a horror film/book and your phone died/has no bars? how boring. I think phones in horror SHOULD work. they should ding only to have the protagonist check and find nothing. they should get calls from somebody you don't know but is still somehow in your contacts. google maps should lead you to one place, no matter what address you type in.
phones are such a big part of our daily lives, removing them from horror removes the horror from our experience. what if the horror felt like it could happen to you, right here, right now? what if it felt like it was already happening?
call 911 and something that is definitely not a person picks up.
call 911 and get an operator only for the call to become increasingly weirder and more sinister until you realize that whatever picked up is not there to help.
text messages from someone who's dead. voicemails that sound like dead air until you turn the volume all the way up.
emergency alerts for weather that doesn't happen on earth.
Your phone rings - but it's your phone number on the screen. You answer it, but all you hear is heavy, laboured breathing. You go to say something, only to hear your voice on the other end tell you "It's too late," and hang up.
You get a message from a number you don't recognise. It's a picture of you from behind. You turn and see there's nobody there. When you look back at your phone, you see the sender has sent another text - "Sorry, wrong number."
Your phone rings - it's a private number. You answer it, only to feel the sensation of something licking your ear.
You wake up to find a voicemail. You play it back, only to hear an autotuned version of your own voice reciting a Bible passage - 1 Peter 2: 18-20.
You get an emergency alert. It says "I'm sorry."
You keep trying to call 911 but you ALSO keep getting robocalls for duct cleaning, surveys, random scam calls and texts.
one time I was in an unfamiliar town, it was 11pm, and I was trying to find some food so I looked up the nearest 24-hour supermarket and started navigation, except instead of a supermarket my phone took me to the gates of a cemetery and then said "you have reached your destination." you could write that incident into a horror movie with zero changes and it scare the audience's faces off