I see a lot of people who propel themselves about the nation and drop whatever they're doing when their phone rings. I tend to laugh.
I've been living here for 6 years and I could not tell you what the house phone number is and, to be honest, should I ever learn it, I won't ever tell anybody else what the number is.
I have a cell phone I bought in the last century, I think. It is still a San Diego # and I get random calls with messages announcing the end of the universe if the wrong number guy doesn't instantly return the call. It goes without saying, I don't bother.
I remember one worthwhile time management course I sat through and the only think I took away from it was never ever answer somebody else's phone. Don't do it.
I had a new boss who was in my office and was trying to puzzle out what my exact role was in the world before time, back when I was running things and we sure as hell didn't have patrol boat officers who surrendered to Iranian surfboards armed with a Persian and a gun. The phone was ringing in the office as we conversed and he wanted to know why I wasn't answering it because, 'dammit, the phone is ringing'!
He was an 05 and I was on 03 at the time and I said, 'why don't you answer it?' It wasn't my phone.
I remember my last conversation with him, many years later, when he was commodore and I was a CO and he asked me if I was going to go to Congress about the issue we were talking about and my answer was, maybe. The phone was right there on his desk.
I answer the phone once a day. That seems to be enough.