Ah, sorry I missed your reply for so long, that is my bad!
It will send the "not in your contacts" number to voicemail, but if they happen to leave one (I would say that 1 in 10 do), you can add them to the blacklist and select "hang up". I personally prefer this since there are times that I do business with folks and I may not know what # they may call me from.
That's how it started "acting up" for me. When I went to look at the settings, I noticed that the FCC database hadn't been updated in quite a while (and refreshing it didn't show a newer date). That's when I went to the app store to see if there was an update and I saw the high number of recent reviews with similar complaints. It really looks like the guy made some decent cash..and well, maybe he went full FIRE.
SO...if that developer is here, right now..YOUR APP SUCKS NOW! I hope you are enjoying retirement!
After I got several calls making it through for a few days straight, I deleted it from my phone.
I now have been using Calls Blacklist for going on week 3 and it has worked flawlessly. Hopefully, I don't jinx it!