To me the most annoying business habit is calling someone when it’s not urgent, even though you have his email address and it should be obvious from your relationship that he prefers email to other means of communication.

I hated phones since I was a wee lad, but I dislike them even more now, because:

1. They break my concentration; rarely for a good reason.
2. They are invasive and inconsiderate. Just because it suits you to call me now, it doesn’t mean it suits me.
3. Whatever is said on the phone can be denied later and sometimes is.

Leave a trail or fuck off.