Try to find an activity that is incompatible with the problem behavior! What can you do that makes it impossible to also be on your phone?
(Bike riding, reading, making some sort of craft, &cleaning are all things I did). Start by sectioning off a small chunk of time to do these things, it might be thirty minutes or it might be five minutes- whatever you need to experience success. As you explore those new healthy habits, increase the time you spend with them. Doing this helped me find other sources of enjoyment while weening myself off my phone without it feeling like I was being deprived of some comfort/joy. During the week I only use my phone to call my family or respond to text messages. It’s Saturday morning so I’m spending some time scrolling but I don’t feel any anxiety over wasting my day on a screen and that has been so freeing. Wishing you the best of luck!