How to end nuisance calls on your mobile

I have activated the DND ( do not disturb) service on my cell through Vodafone, however, I still get SMS's from all kinds of people including Dr Batra whose homeopathic pills promise to relieve me of piles and baldness and variety of diseases which I have not heard of. Sometimes there are calls when I am in meetings and my battery is about to die from Share Khan whose representative thinks I should play the stock market by giving his company  access to my funds:) I was therefore relieved and happy to see this link which promises succor for harassed souls like me :).

http://news.in.msn.com/national/article.aspx?cp-documentid=4661213

The only option till now was to act funny like the radio host "ghantal" and irritate the caller! A sample of this funny call is attached below:)
http://mayanmuse.blogspot.com/2010/05/call-centres-in-india-very-important.html

INDIA : THE RURAL BPO.

http://knowledge.wharton.upenn.edu/india/article.cfm;jsessionid=a830ab3a44fb5a82fbac91e3a12315017242?articleid=4450

With spiralling real estate costs in metros and urban centres and improved IT infrastructure, BPO's are shifting to small towns in India, where salaries too are much lower.