Airtel — dnd not in effect in spite of registering for 0 ads from april 3

Address:	Bangalore, Karnataka, 560100
Website:	www.airtel.in

I have registered for dnd very long back. To be specific on 3rd april and got confirmation that the changes will be effective from within 7 days and yet i continue to receive ad message which i have subscribed to till date from companies such as foodpanda, the princeton review etc., why was dnd not in effect all this while inspite of getting confirmation that dnd is registered with "fully blocked" setting? Why was i still receiving ad messages all this while? Is this how airtel makes ad revenue?