I don't even have my office phone regularly connected. It's tied to our e-mail accounts, though, so if someone calls, I get an e-mail (that contains a voicemail if they leave one). If it is someone I need to talk to, I set it back up and call them. Fortunately, this only happens about once or twice per year. The rest of the time, we talk in person or via e-mail.
This doesn't include research collaborators, though, who I talk with on my cell phone if we need to discuss our projects. I consider those a bit of a different case, though, since we often do need to talk about things where e-mail wouldn't suffice and we're spread throughout the country.
I generally dislike the phone, though. The only people I talk to regularly on it are my parents and my brother, who live far from me, so it is the only way to easily stay in touch. Even other people, like my good friends and roommates from college, that I want to keep in touch with, I don't pick up the phone to call.