Called my office phone but no message left, just dead air.

They don't id who they are  - it is an automated voice that says  press 1 now.... Then it says press 9 if you want to be removed from this calling list.....    I wouldn't press anything because that will confirm a number that reaches humans !!!  Which is what they want....

Called my business.  Dead air and then they hung up.

Called our business.  Nobody on the other end.  Hangs up itself before anybody tries to speak.