Tata - I hate you

Well, do not go by the title. It is about the advertising calls we get on mobile everyday. I get regular calls from them, I have Tatas connection, CDMA one. The numbers start with 6 or specifically 600, in the morning around 9 am and in the afternoon, they never miss the chance to irritate me, I registered for Do not Disturb long back, through their web site, but it dint work. I think they want us to send SMS and spend some more money to block the calls, I think you guys also get same calls, have you ever tried sending SMS (DND) to the number they provide and see if it really stops.