Block people without called ID

On the iPhone it's super easy to block someone whose number is shown, just tap the ℹ and choose block, but there doesn't seem to be a way to block people without called id. The info page is just blank! Is there a way to do this? I'm pretty sure I know who it is too, I blocked this jerk last week, and now I get (for the first time) a "No Caller ID" call last night.