Hmmm Raj even i get such annoying messages in Airtel! Though i have adjusted living with it , because if i de-activate it i will not get any offer messages on talktime and other services from Airtel!
Try blasting them once explaining your position!
Even when i used BSNL i used to get live score updates for free even though i have not subscribed to it. BSNL is really good in this DND service. My mom using one activated it and she stopped getting such messages and calls right from the next day!