Extremely important question for the truly smart people?

Question

What does it usually mean when you call a # and it says that it is not in service for incoming call?

Answer 1

either the mailbox is full or incoming calls are blocked or they have a technical issue with  phone service.

Answer 2

its a phone booth

Answer 3

maybe the phone is off, or engaged.

Answer 4

Normally this is due to the person not paying their bill. They can still make emergency calls but that is it.