複数の SIM/eSIM を同時に使用する場合があると思います。どの SIM がデータを使用しているかを確認する方法は次のとおりです。

Apple (iOS) Devices

Go to:

  • Settings  → Mobile Data  
  • Here you can see which SIM is currently using the data and can further enter that menu to change it.

Android Devices

Go to:

  • Settings  → SIM Manager → Mobile Data
  • Here you can see which SIM is currently using the data and can further enter that menu to change it.