PSA, if someone asks you for contact info (e.g. a phone number) of someone you know, the correct response is "I can't give that to you, but I can give them yours".
It's efficient and adds no round-trips, it's privacy friendly, it's non-awkward and it's social engineering resistant. It's a universally good rule.
And the corollary, of course: Don't ask someone for another person's contact info - ask them to pass on yours.
@Merovius I avoid giving out my smartphone number- or even my email address- because of extreme and chronic social anxiety/stranger danger resulting from some horrible stuff I went through in my formative years, but even if I hadn't I would still feel uncomfortable doing so, and more uncomfortable than I do refusing to give private contact details out to others.
I definitely don't share the private contact details of people I know with another person if I'm asked, at least without permission.
Merovius
Twopaw