There is an app called NQ Call Blocker, if you don't have the option on your phone. It's free and super simple... For people you know but don't like, you can choose between blocking calls, texts, or both... Awesome app!
Calls several times a day but leaves no message, and hangs up when I try to answer. I called back and got a recorded message about auto loans, and a message to press 1 for more info, 2 to be removed. I pressed 2, we'll see what happens.