Reliance Jio is 4G only network across pan India. It’s a powerful network with a great infrastructure to conquer the Indian market. But you need a 4G enabled smartphone device to access this network for data. But for voice calls you need to have an extra feature that’s voLTE.
But not all old smartphone devices comes with the feature hence Reliance Jio made it possible for the user to enable this via the application, Jio4GVoice.