I use a Bluetooth earpiece when driving so my hands are free. I resisted buying a cell phone, especially since it is an extra expense in addition to my telephone, but, when I got a sales job that makes me work out of my car and be on the road, I had to get a cell phone. My customers, my manager and my co-workers, family and friends would not be able to reach me unless I have a cell phone. It would be impossible to do my job without one, as I have to be able to call people and receive calls even when I am traveling.
If I get a call in a store, restaurant or other public place, I speak quietly and try to find a corner or go outside so I don't bother other people around me with my conversations. If I can tell by the ring I've designated that it is a co-worker, I often let it go to voicemail and then call back later when I'm not driving or involved with something.