I will not recommend jio4GVoice for calling purpose .
Because it lags some times, some times call get dropped.
For use it you have to turn on your data unless without data it is not gonna work.
Your mobile dosen’t need this app if your mobile is volte enabled.
But if your mobile is not volte enabled then you dont have any option you have to use it for free calling purpose.
This app works only on jio 4g if you try to use this app with any other telecom operator then it is not gonna work .