How to restrict who can call you on the iPhone 5?

How do you restrict the people who can call you to just your contacts? I get a Lott of wrong numbers and it gets annoying. I can't find the security settings in my phone.

Go to your settings app, choose do not disturb and then select who can get through from the options everyone else won't be able to. You can choose only your contacts or only those marked in your VIP or favourites.

Or you can choose no one can get through.