Yep, that's why I can't stand this arrangement. Respect others time and workflow by using non-blocking communication like email or IM. They'll answer when it's convenient for them.
I always preferred IM or email to phone or face-to-face for this exact reason. IM and email can be ignored until its convenient to reply, but phone and face-to-face forces you to stop working and respond right away, even if you were right in the middle of something.
