Your Surface Duo supports both physical SIM cards and eSIMs. If your carrier supports it, eSIM makes switching between mobile carriers and data plans really easy. It’s especially useful if you rely on multiple carriers or data plans for different occasions, such as a work and personal plans.
eSIM can be used in conjunction with a physical SIM, or alone. Check out the tutorial below that walks you through connecting to your mobile carrier via an eSIM.
Connect an eSIM
Assuming you have already applied to an eSIM from your carrier, they should have provided you with a QR Code. If you’ve lost it, you’ll need to contact your carrier to have them resend it. Keep your QR code ready as you’ll need it.
Step 1: Make sure your Surface Duo is connected to Wi-Fi.
Step 2: Go to Settings > Network & Internet.
Step 3: Tap + next to Mobile network if you have a physical SIM inserted, or tap Mobile network if you don’t have a physical SIM inserted.
Step 4: Next tap Download a SIM instead. If it asks to Use 2 SIMs, tap No thanks.
Step 5: Hit next on the Download your SIM screen.
Step 6: Scan the QR code provided by your carrier and follow any instructions to complete the connection.
Switching data plans
Switching plans can be done through Settings > Network & Internet > Mobile network.
Note: To use the data plan on your eSIM, you will need to remove the physical SIM from your Surface Duo.
The Surface Guide 
Hello, In step #3, you say “Step 3: Tap Mobile network if you don’t have a physical SIM inserted.” Mobile Network is NOT an option in my Surface Duo. Plus Surface Duo is unable to read the QR Code from the cellular provider. I don’t anyone has the same issue I have. Any help?