Emails: permanent written record I can refer to later
Can reply in my own time
Low labour
Low resource use
Phone call: Times/dates mentioned will be forgotten often
Active demand of time
I don't pick up because that phone number looks weird but also my phone's vibrate function is weak
High labour
High data cost per information
My shrink's office seems to want to keep billing information and past/present appointments secret. (This also seems to be worse in local industry, everything has to be a meeting instead of a two line email)
Emails are so much more annoying to troubleshoot whenever I get a client sending us an email saying "X and Y is BROKEN". It's equally annoying on a phone call - but at least then I have them physically by the ear and can hear the lie in their voice when I go "and have you tried a different browser?"
Of course, because I don't really mind phone calls - they have become my responsibility so I am fully 100% with you that we need to switch fully to email.
I don't think we need to switch fully to email, I just think phone is unnecessarily preferenced. :/