If it's important, leave a message.  If not, don't call back.

No response to answering machine ... number is now blocked.

Called my cell, I have the Blacklist app and previously id'd this number and it worked! When a number calls your cell that had been previously id'd your phone does a half ring, hangs up for you, and puts it on a log tjat you can check.  I put my nosey [***] sister in law on the list, works great. I highly recommend it!