I just discovered this app for my iPhone and I love it. It’s called Mr. Number and it provides call blocking and Spam protection. It is made by Hiya Inc. and was released for iOS October 29, 2015. It works with iOS 7 and greater on iPhone, iPad, or iPod touch. It is free.
Mr. Number icon
I personally never answer any call that has an 800 number and no name identifier. But, they call back, over and over. It’s all automated. Now, the first time I get a call like that I can do a reverse look-up and then block it, or just block it.
When I get an unwanted call I write down the number and then open Mr. Number. I look it up or just block it and it retains a list of my actions.
If you have this problem then by all means check out the app.
NOTE: I forgot something important when I wrote this. You have to actually turn on Mr. Number in Setting before it blocks the calls for you. Select Settings > Phone > Call Blocking & Identification. You should see the icon for Mr. Number. Be sure you move the button to turn it on. It doesn’t happen automatically.