it's a service called privacy manager you get from your phone company.

Here it was called anonymous call rejection.

If your switch codes are the same as ours, you dial a *77 to activate anonymous call rejection.  This is to balance people who SPECIFICALLY use a *67 to block their caller id information or who have, in some areas, their information blocked on every call i.e. "private".  

You may still receive "unavailable" calls if the caller id information simply isn't sent with the call (as opposed to deliberately using *67).

Usually your features are all explained in the front of the white pages.  We (I work at Verizon) are no longer allowed to print the feature codes and instructions in our phone books because other local carriers whined to the FCC saying it was competitively unfair.  

can you hear me now?

can you hear me now?
[:)] someone had to say it!!!!!