Calls from "international" may be friends who don't use Skype. AFAIK there's no qualifying CLI data to differentiate them from cold callers.
Calls from "withheld" can be the doctors' surgery or the local council.
All of whom can at least respond to a call-screening answering machine with "Hi xxx, this is yyy from zzz, I'll call back in 5 minutes". No need to give away anything personal ("It's about your STD check") and you can either pick up during the message, or answer when they call back.
Biting the hand that feeds IT
