This is a quick guide on how to enable VoLTE and VoWIFI on every OnePlus 8 or 8 Pro device.
This method involves downgrading the OnePlus LogKit APK to the OnePlus 7 version.
I recommend you to backup the existing LogKit APK using ADB on a
Or download an APK extractor from the Play Store, i personally recommend: https://play.google.com/store/apps/details?id=com.ext.ui&hl=nl
After you extracted the original LogKit you need to download the old LogKit which you can find as an attachment in the thread.
Install the downloaded LogKit APK and follow the steps:
1. Open the Dialer app on the device.
2. dial *#800# and LogKit will open up.
3. Scroll all the way down and click on Function Switch (this is missing from the stock OnePlus 8 LogKit APK).
4. Select VoLTE and when prompted to reboot, press cancel.
5. Select VoWifi and when prompted to reboot press OK.
6. Your device will now reboot and you should have VoLTE & VoWifi enabled.
7. Reinstall the backup from the LogKit apk (VoLTE & VoWifi should still be enabled when you reinstall the backed up LogKit apk).
The above has been tested to work in The Netherlands.
If you have followed the steps, please let me know what your results are!
WiFi Calling Screenshot:
For people experiencing problems with receiving calls when having 2 sim cards installed. The above steps seem to fix this issue.