In this guide, we let you know how to enable VoWiFi for Jio SIM in Asus 6z. Asus has not yet enabled the service in Asus 6z units sold in India. The OEMs need to release an OTA update to make it compatible, but there is a workaround for now. To enable VoWiFi for Jio in Asus 6z (ZenFone 6), dial the code ##3642623344## You will get WiFi calling option in the Call settings. Turn on it for Jio SIM. Several users have reported this is working on their device. To work it properly, first, you need to deactivate the VoLTE/Enhanced calling switch, then activate WiFi calling and then activate the VoLTE switch after getting a WiFi calling symbol. Also, you need to repeat the above steps after every restart of the phone. FYI, VoWiFi (voice over WiFi) service allows you to make crystal clear calls to any network, regardless of network signal strength. Though WiFi calling hardware is available on most of the smartphones, OEMs need to release a software update to make it compatible. Here’s how to enable it in Xiaomi phones and OnePlus phones (Source)
