As far as I know I've been on whatever passes for a DND list in India.. Its upto my service provider Idea to make sure i don't get unsolicited calls..
Here's a perfect reason for them to take it more seriously!
Listen to the call I got -
In case you would like to be added to the DND list, heres my old post(from 2012) about that - http://chaitanyakrishnan.blogspot.com/2012/03/how-to-block-unwanted-calls-and-sms-in.html
Note: both DND and NCPR registeration will happen with expicit knowledge/cooperation/whatever of your service provider.. so ya.. its probably not going to block 100% of those stupid calls.