blocked calls

Notifying the caller of a blocked call depends on your call blocker.  Some call blockers offer this feature and some do not.

If your call blocker offers this feature, it will answer the call from a blocked number and play a message.  The message(s) could already be installed on the call blocker...or allow you to record a message...or, if connected to the Internet, allow you to download audio files.

If you don't have this feature on your call blocker, the caller will usually hear one ring and then the line goes dead.  I like this option because it just confuses the caller.

If you're using Cox Selective Call Rejection, the caller will "...hear an announcement that you're not accepting calls at this time."  You could test it by temporarily blocking one of your phone numbers and then calling your Cox number.