Add all the numbers which you don’t want to receive calls to “Black List”. To do so, you need to activate this service by calling 55144 or dialing *514# from your phone. Activation of service takes up to 24 hours . After activation user can create black list by entering 10 digit mobile number & for non-mobile numbers, enter numbers with STD code starting from ZERO.
Add numbers to white list which you want to receive calls. Others numbers will not be able to call you. This will be helpful while in roaming, where you can receive calls only from people you choose.
Black List & White List both cannot be active at once. This service is charged Rs. 99 / Month which I think expensive for average users.