You know, just because you have a cell phone with you doesn't mean that you have to have it on at every moment, nor do you have to answer it everytime it rings. If I am waiting for an important call and I am in the company of someone important to me, I turn it off and pick up the message later (maybe excuse myself to go to the restroom). If it is a call that I have to take, I will excuse myself, get up and walk away to a private area to take the call.
What did people do before they had cell phones and felt the need to take each and every call? I'm always left with the impression that they want other people to see how important they think they are. Believe it or not, it can be good not to be 110% accessible to all calls. People need to understand that you, too, have a life!