Promotional calls are like nightmares, if promotional calls are allowed on your mobile number. One of my friend has not registered his number under DND, he is using Uninor SIM card he get so many calls from Uninor. A day he got 8 missed calls in just half an hour, missed calls because he had not received any calls.
To get rid of promotional calls you must register your mobile number for DND. TRAI has many strict rules for promotional calls and SMS, otherwise users were victim of service provider company along with other promotional calls and SMS.
So TRAI has made clear rules to identify promotional calls so you can identify these calls without receiving. Now all the promotional calls start with 911 as 911402310576. If you see a number is starting with 911 you are sure it is a promotional call from your service provider or any other company.