For Volte to work Samsung has to partner with your carrier to enable it with a firmware update which will give you the options in settings. if your network is Volte enable best is to get a Volte ready device that doesn't need CSC to work.
I'm using JIO sim which only works on Volte enable devices. My friend using same mobile J7 Pro (J730GM) which support volte. I'm using J7 Pro (J730F/DS) imported from UAE which is not supporting volte.