I found a free application to block your unwanted incoming calls:http://www.logic-unlimited.in/callfirewall.php
Features:
a. Accecpt all calls
b. Accept call from My Contacts only.
c. Reject all calls
d. White List - accepts calls only from the white listed.
e. Black List - accepts all calls except from the black listed.
f. There is also an option to reply with an SMS.
