Jio4GVoice. This is well thought for calling using 3G phones. It is used to call using JioFi. It gets connected to phone and allows the user call using the Jio sim in JioFi device.
I have bought JioFi Device as I was having 3 Android phones and all of them was 3G. Using this app I have enjoyed the free service till March 2017 and then recharged and is still using Jio.Luv the concept.