OnePlus 6 and 6T support Dual SIM with both SIM use 4G network. It’s very useful when you like mobile network information to Cellmapper. But you see second SIM does not use 4G by default if you do not have VoLTE enabled. That is reason because why phone like use 4G if you do not use data or calling services on 4G.
So you must enable VoLTE on your phone settings to keep your phone on 4G/LTE. But don’t worry, you do not need VoLTE subscription or if your carrier does not support VoLTE, it’s fine. You just need enable VoLTE on your phone settings only.
This instruction only enable VoLTE on your phone settings but does not enable VoLTE subscription. If in phone there is no correct settings, VoLTE does not work. You can check your provider VoLTE support on your provider customer support.
Your SIM must have permission to access 4G network and on your area must have 4G coverage. Otherwise phone use 2G/3G networks.
So let’s start:
- Open Dialer (Phone App)
- Select Enter on warning message.
- Call to USS Code *#800#
- Go to opePlus Logkit
- Swipe down to Function Switch.
- Tick VoLTE and VoWIFI wifi enabled.
- Reboot your phone.
- After reboot, check on Android Settings -> SIM & network -> SIM 2 (Your provider name, example my provider is DNA) have VoLTE toggle enabled.
If you have VoLTE / VoWIFI subscription you maybe see VoLTE 2 icon appear if phone load config, but on my network does not work. On DNA phone does not work VoLTE on second SIM. But without icon it just mean does not register but it’s fine for recording data to Cellmapper.
- Now open Cellmapper app and if your area have 4G/LTE for your second SIM you able see both networks on 4G/LTE same time.
- On CM App you only need enable Cellular API 4.2+ . Do not enable “Dual SIM” settings on app settings.
When you receive calling to second SIM phone where is no VoLTE subscription, phone will automatic drop 4G to 3G this second SIM and you can talk normally. When calling ends phone will choose 4G back normally.