Rob, do you use a standard (wired) telephone service?
Is your number listed in the white pages?
I have used VOIP for my telephone service for a LONG time now.
The number does not appear in any telephone book.
It is not one of the usual sequence of numbers that are easily programmed in to a ‘dialler’ used by those trying to ‘get at you’.
Calls such as you describe are, for me, rare to never.
On those rarer than rare occasions, I listen politely for a short time, then quietly hang up without making any comment.
I hope this information is of some use to you.