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Spoiledbrat Not all telephones have that feature (mine doesn't so I have to interrogate it after the call to find the number) but sometimes you receive calls from what look like genuine numbers.
Perhaps it seems one you have used only once or twice, e.g, a mail-order company or a travel booking-office, but forgotten? Or is it from a fellow member who does not normally ring you, of a hobby club with a geographically widely-scattered membership?* A genuine caller would be expected to leave a message.
There, the number has been "spoofed" to resemble a real one from your own country, or is routed through a sort of accommodation number, but is actually from anywhere in the world. It might be the telephone equivalent of those fraud-attempt e-posts pretending to be from a friend or relative, asking for an emergency loan.
Sometimes the area code alone is the give-away by not looking right for your own land - well, it isn't!
The telephone companies seem unable, unwilling or just too complacent to prevent this happening and act properly against this sort of misuse of the system.
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*(Clubs and societies used to publish personal telephone numbers for enquiries, but many now use a web-site instead, in which the enquiry will be routed through something like "appropriate-officer-title@ yyyyyy-xxxxxxing-club.org", for both security and longevity.)