Microsoft is pulling the plug on Cortana iOS and Android apps. Support for the app will be dropped from 31 January 2020 in several countries, including India.
Unlike Siri on iOS or Google Assistant for Android, Microsoft's virtual assistant Cortana isn't integrated into either operating system and functioned as a separate app. On Android, you could invoke Cortana faster by using Microsoft's launcher, but Cortana is being pulled from that app as well.
The app will find a new home in the new Office365 app from Microsoft, and its functions, such as syncing to-do lists, will be taken over by dedicated apps.
On the whole, this really isn't that much of a loss given that Cortana really isn't that popular.