[Osem]

Well they're another, highly annoying, issue but once you've spoken to someone about an important matter the clock has started ticking and I think they're more likely to act promptly if only because they've been made aware of the issue - something which wouldn't be apparent until an email had been opened and read. What I tend to do is make the call then follow it up with an email confirming the name, date and time of call. I wouldn't rely on just one approach or the other for something I considered important and/or urgent.