I was will confirm the private and personal line works. My father was previously an elder and he is the one who put me on to that phrase when I was still in.
Whenever anyone tried to stick their nose in my business this was the nice way of saying mind your own business.
If they push it shake your head, smile, then say “I’m sorry but this is a private matter not open for discussion”. And walk away, hang up the phone or close the door.