Please tell us some basic information before asking for help:
Model Name: 6z
Firmware Version: 194_0
Rooted or not: not
Frequency of Occurrence: NA
APP Name & APP Version: NA
In addition to information above, please also provide as much details as you can, e.g., using scenario, what troubleshooting you've already done, screenshot, etc.
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Enable VoWiFi for Airtel carrier,