If it were up to me, I'd do all my work communication via e-mail. E-mail is great because you can get the benefit of prior discussions in the string, relevant documents and materials as attachments, and a message that someone has thought about enough to put down in writing. I like to look at my e-mails first thing in the morning and prioritize them and work off of my in-box. If I can't get to something the same day, I at least acknowledge it with a projected return date.
Occasionally, I'll encounter a dinosaur who insists on using the phone when an e-mail would do. I hate that. I have come to regard non-emergency phone calls or non-privileged calls as the epitome of rudeness. It is like saying DROP EVERYTHING AND ATTEND TO ME NOW BECAUSE I AM MORE IMPORTANT THAN ANYTHING ELSE YOU COULD POSSIBLY BE DOING RIGHT NOW. I almost always answer my phone, so it's really a bother when it's something routine. I frequently give people the brush off and make then set up an appointment to call at a set time if they can't e-mail me. I have begun to treat phone calls the same as in person appointments. They are both drains on productivity.