1. If it is registered on DND Registry or not (What is the DND registry? – Read more on our SMS Guidelines post )
2. Which telecom operator the phone number belongs to (e.g. Airtel, Aircel, TATA, Reliance, Vodafone etc.)
3. Which region (state) does the phone number belong to also (e.g. Karnataka, Tamil Nadu etc.)
Hope it helps.