I only enable mobile data when I need to sync calendars.
That being said: on PC and too often check hacker news and similar sites: I'm trying out Krishnamurti's "observation":
Can you catch yourself the VERY MOMENT you wish to go to some website (NOT after you already did: but when you wish to go: what kind of pressure/frustration is building up in you?
I feel like the next step after recognizing and slowing/stopping the problem is with filling that void with meaningful work. For this I recommend "Deep Work" by Cal Newport. I felt like that book gave me the tools I needed to not just stop the bad habit, but replace it with constructive ones
Maybe disabling data on the phone will be a good way to do it! (I still need to keep it around at work hours for calls.)
There's a lot of external pressure to be constantly on your phone. People of my age are a little perplexed when I explain to them the reason I didn't text back right away was because I was outside, but my phone was upstairs in my room.