sometimes it’s if someone calls and I need time to myself I’ll still pick up.
Start here. Baby steps is the best way IMO. Next time someone calls, make a decision to do just one thing before answering, ask yourself: do I need time for myself right this minute?
If no, answer the call.
If yes, don't touch the phone, don't look at who's calling, just walk away.
I assume you have voicemail? If so, let it be used. I use it often to screen calls. If a person calls multiple times, and I know the person, then I may look at it incase of emergency, however, if a person did that just to get my attention, then I never answer them again when they do that, emergency or not, and the call goes to voicemail.
The phone stresses me out. If it wasn't for my wife, I wouldn't have one. It is 100% only due to her that I have one, as she wants to be able to contact me when she wants. I can't argue with that... but everyone else? Nope.
Baby steps, do something small, do it enough times, let it become habit. Review what you accomplish, any failures, adapt. When you become better at accepting to do this yourself, without any guilt, move onto any toxic friends and remove them from your life, and the best way for that is usually, exit immediately and block them from every and any source. I will agree though, you need to be pretty comfortable within yourself to do that without issue. I am good to do that, and have done it. I wanted a clean break from my past, so everyone bar my absolute best mate, all gone from my life in one go.