https://support.google.com/fi/answer/7540641?hl=en
官网解释，简单的说，如果你有Pixel 3 or Pixel 2 ，按照激活提示来就可以了。
如果你已经激活了，那么就在物理卡和esim之间切换一下就可以了
Switch between your eSIM and physical SIM card
If you set up your Google Fi eSIM and also have a physical SIM card for a different carrier, you can switch between mobile networks.
Open your phone's Settings Settings appapp.
Tap Mobile Network.
Choose the name of the carrier you'd like to use.
Tap Switch.