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)