Use root Explorer end go to this line in :
version/special_cust/ANE-L21/hw/en/prop/local.prop
Write this and you have volte ?
ro.config.hw_volte_on=true
ro.config.hw_vowifi=true
ro.config.hw_vowifi_mmsut=true
ro.config.hw_volte_dyn=false
ro.config.hw_volte_show_switch=true...