Anyone found a way to block unknown numbers?

Ok guys, put here but could go in beta as well I suppose.

Whilst I know how to block a number in the phone app I can't find a sensible way to block an unknown number in the new unknown callers feature. The only way I have found to do this is to change the number to known then block as usual which seems a silly way of doing it. I don't think this is a bug so was wondering if anyone has managed to find a block option. If not then this is a miss by Apple and needs changing.