Called our private unpublished work number. Did not leave a message. Comes up Wireless Caller.

This number called our private business line again today and again left no message so I called it back and the message says that the number has been changed or disconnected. I wonder how they're able to get that message from a line that just called us 30 seconds before? Hmmm

Google Voice can do it - they just program in your number to be blocked.
https://support.google.com/voice/answer/115089?hl=en
Block unwanted calls, abuse, and spam
...
Block Caller: The caller will hear a "Number not in service" message when calling your Google number. None of your phones will ring. Blocked calls won't show in your call history as missed calls.

Other VOIP telephone services can do the same.

This number calls me about every 3 weeks, but when you answer, music begins to play.  Just very strange.  Why do they bother, just annoying.

Try not answering unknown calls-maybe they'll stop calling you.