Just FYI:

To help with all the annoying telemarketing calls I've been getting, I took the following steps on my iPhone.

• In Settings --> Sounds I assigned a very soft, weak ring as the default for incoming phone calls. I used Chimes because I can barely hear it.
• For each nuisance call I get, in Phone --> Recents I assign the phone number to my Ignore contact wherein I set the ring tone to Silent and the vibrations and tone for text to None. (To add a caller number to Ignore press the Info icon, an "i" inside of a circle, on the right side of the entry line.)
• In Phone --> Favorites I set up a Favorites list which contains any contact from which I will accept calls.
• I assigned each Favorites list contact a loud ring such as Old Phone.

Now when I get a new unwanted call the phone is barely heard when ringing. My acceptable calls have a loud ring. My Ignore calls are totally silent. So far this method seems to be working, though rather kluge to set up. It would be better if Apple would simply give us some phone options like Silence All Unknown Calls.