When it says on your call display unknown id, does that mean it's a unlisted number and how do you find out

Question

the number?

Answer 1

There is a feature called Per call block which would prevent the display of the  number that is calling you, if the caller  dials a star code and dials your number then his/her number wont be dislayed on your Id

eg *67xxx-x*x-xxxx

and you can find this out if you have Call trace feature

you have to dial a star code eg *57 immediately you receive this call and intimate your service provider.

Answer 2

It's not unlisted #. It's the people who called you don't want you to know their #. There's no way you can find out the # unless they tell you.