its impossible to block missd calls..
but i have gr8 idea for that no need of mobile phone off...or any other....

go to ur mobile phone settings...then..call settings..... their u can get...any key answer... its already off.. but u on it... and when u got any ring press early any button... 2 or 3 times when u pick his phones next time he not misd call u......
if mobile phone is in ur pocket u can press any button its phone received....