There are times I need an immediate answer, but the need for an audit trial over-rides the immediacy of need. In those cases I go to email, not pickup the phone.
My overwhelming preference in business is email, reason #1 above (audit trial), reason #2 is while I know what time zones co- relate to what area/country codes, yesterday I was able to make a phone call from my cell phone in another country and a few times zones out, simply by using wifi calling from where I was. The act of globalization means that you may be able to reach me on my phone during business hours, but my hours may be different from yours, and I may not always broadcast where I am.
One of my other favorite rules is that I don't assume all is well in someone else's life. Business is important, but if my mother, or one of my kids is sick and dying, kima-yoyo
(kiss my ass, you're on your own
) So I also try to be understanding that the other human I am interacting with has human issues that he/she may have fall in their lap in the middle of the deal.