From which operator were you calling?
When I call from my Vodafone number to any other operator, if other number is out of coverage, I hear that Vodafone number is out of coverage even if number I called is not Vodafone. I have no idea why this message is heard.
But hearing AT&T is weird. AT&T relationship with India ended after it sold its stake from IDEA many years ago.
Regarding Vodafone, they are doing good in India, so I doubt they will be selling their
business.