I'm fairly new to GrapheneOS, had it for about a month now. I have been able to make/receive phone calls through Tmobile without cell data turned on since I got on Graphene... I assumed it was because of wifi calling that phone calls are working. So I always leave my data (drop-down menu -> Internet -> Mobile data) turned off when at home.

So today, I walked to the store but forgot to turn data on. I get to the store and while at the store I make a few phone calls...which went through without any issues. Then I get home and realize I had cell data turned off! So, how are calls working if i have cell data turned off??? I have no wifi setup or turned on either except at home

It seems like the data toggle in the internet menu is broken? Or is there something I'm missing? I'm also wondering now if when i make/receive calls at home if its NOT wifi calling...but still using data maybe (while data is turned off). My provider is tmobile. Thanks

I just reproduced it

I have mobile data turned off and i turned wifi off

i am able to place a call to a regular phone number

Is there maybe a setting for this?

    dimyself So how that works is the toggle for mobile data is just that "data". To stop your phone from calling you'll have to use airplane mode. That will disable calls as well as everything else.

    Ahh ok, i must've misunderstood.

    When I have mobile data toggle off, "4g" and "5g" labels also disappear from the top info bar, which makes it look like no carrier stuff is working.

    Just to make sure i understand... if I have mobile data off, my phone is still hitting cell towers because mobile data is different from phone calls? Is it using 4g or 5g for phone calls (with mobile data off)?

    And if i have airplane mode on and wifi on, then mobile data and phone calls are off?

    ** i just tried a test... i have it in airplane mode, but have wifi on. I'm still able to place a cell phone call through the phone app. Is this wifi calling?

    Is there a way I can tell when i place a call if its using cell data or wifi calling? And if i use wifi calling (with airplane mode on and mobile data off) to place a call, is it going through tmobile cell towers then, or through my router/internet traffic data?

    thank you

      dimyself If you put your phone in airplane mode and turned on WiFi, you have disabled connection with towers and are using WiFi to make calls.