I prefer emails and Instant messenger and AFTER I have some picture about the aff manager and I am asked, we can have a chat on the phone.
Nothing is more annoying than working on something really hard, you have the idea, you just need to write it down for example for an article and then baaaammm, phone rings and takes your attention away.
I have read an interesting article some months ago http://www.thinkvitamin.com/features/webapps/how-to-shut-up-and-get-to-work and then I found another article about interruption during your work can cause you to lose 10-30 more minutes to get back to your work, and I had to realize that the most productive time of my day when I don’t accept any phone calls, I don’t open the IMs, and I keep Outlook untouched. 
So I made 2-3 hours of my day like this, it works like a charm