Ok. I did some search myself. It does suggest that passengers can receive the phone call, which means that phone can be switched on if there is a passenger, otherwise, it should be switched off.
See last two questions at
Driving Tips, Precautions During Driving F.A.Q - Indian Driving Schools
Other links that I read are:
Public service ads don’t work but jail does! A wide angle view of India List of countries that ban cellphone use while driving