I want block unknown callers from iPhone 5

There is no way to do that. If you are receiving unwanted calls see if your carrier can help you

If you mean calls that say UNKNOWN, copy just UNKNOWN and in the blocked caller list add UNKNOWN by pasting it where the number goes. Works for me.

that is not possible to do on the iPhone 5s, so I'm pretty sure the 5 doesn't accept that as well. It makes you add a actually phone number or one from the contact's list.., but a number Non-the-less...Sorry but this doesn't work. Thanks for trying though.

OMG there's one of you geniuses chiming in on every one of these topics.

To quote from one of my all time favorite commercials:

Seriously though, how simple minded do you have to be to think that adding a contact named "Unknown" or "Unknown Caller" and blocking that contact would work to block calls with no caller id. Like, I never comment on stuff online, but the idea that this level of stupidity exists in the world is just angering to me. I know I'm not offering a solution myself, but at least I'm not offering a useless, moronic one.

But why are you so mad about it. Seriously.