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)
What weirds me out is when customers prefer phone calls to emails. They want your assurance that an issue is being handled, they ask you to insist that you'll remember to call them back, and like, my note system is just scrawlings in Windows Notepad. If its in email, my boss sees it and I have a ledgerof undone tasks with timestamps. Asking me to manually do it all on the phone is begging me to lose it, or if I hate to, to intentionally fail to do it. That's much harder to do in email