How to Block All incoming calls without a third party app

It's not a magic.
This is an easy way to block all incoming calls without any third party application.

Go Settings>Call Settings>Call forwarding


Now select ALWAYS FORWARD under the CALL FORWARDING.

Type a wrong number(you can use disconnected phone number or any other wrong number  here ) and save it.
When some one call you it will be forward to that given wrong number.

Now no calls!