Block calls from unknown and withheld How can I block calls from the "Unknown" caller? I have iOS 7 on an iPhone 4S. Does any other version of the iPhone offer this ability?

I've checked the question Call blocking for iPhone?, but it doesn't seem to work for "Unknown" callers.

I found the following question: Cannot answer unknown calls on my new iPhone 4S.

I want to do the opposite. I want to stop unknown callers from coming up on the phone, and I would rather not know that they are calling.
Sorry, but true call blocking can be only done by a carrier. However, if you wish to allow calls only from your contact list, and exclude everyone else, you can use Do Not Disturb feature on your iPhone 4s.