Vietnam eSIM on Samsung Galaxy S25 Ultra – Setup & Dual SIM

The Samsung Galaxy S25 Ultra — available in US, EU, Korea, China, and other markets — includes full eSIM support with dual SIM functionality. This means you can use either one physical SIM plus one eSIM, or two eSIMs at the same time. The model number SM-S938x always has eSIM built into the hardware; there is no carrier lock for eSIM on most regional variants, though some US carrier-locked units (e.g., from Verizon or AT&T) may restrict eSIM usage on certain networks.

To verify that your device is ready for a Vietnam eSIM, go to Settings → Connections → SIM card manager. If you see the option “Add eSIM,” your phone is compatible. Viettel, Vinaphone, and Mobifone eSIMs we sell work on the Galaxy S25 Ultra without any APN modification — the network settings are configured automatically when the profile downloads. This is true for all global versions of the phone.

After purchasing a Vietnam eSIM plan from our site, you will receive a QR code via email within minutes. We recommend scanning the QR code before you depart, while you still have a Wi-Fi connection at home or in the airport. On your Galaxy S25 Ultra, open Settings → Connections → SIM card manager → Tap “Add eSIM” → Select “Scan QR code from service provider” and point the camera at the QR code in your email.

If prompted, enter the confirmation code that was provided alongside the QR code. The eSIM profile will then download and activate automatically. You can label the eSIM (for example, “Vietnam Data”) in the SIM card manager to keep it distinct from your home line. After installation, set the Vietnam eSIM as the default for mobile data; your home SIM can remain active for calls and SMS at no extra cost. That’s it — you’re ready to use data in Vietnam.

To get both your home physical SIM and the Vietnam eSIM working together, go to Settings → Connections → SIM card manager. Here you will see “SIM 1” (your home SIM) and “SIM 2” (the Vietnam eSIM). Under “Preferred SIMs,” set “Mobile data” to the Vietnam eSIM so all internet traffic goes through your local plan. For “Calls,” keep your home SIM selected if you want to receive calls on your regular number (IDD rates will apply), or switch to the Vietnam SIM if you need to make local calls. The “Dual SIM Always On” feature is enabled by default, ensuring both lines remain reachable.

The Galaxy S25 Ultra supports 5G SA (Standalone) on both Viettel and Vinaphone networks, so you can enjoy high-speed data. Ensure your network mode is set to 5G/LTE/3G/2G auto in Settings → Connections → Mobile networks. If you receive incoming calls on your home SIM while using data on the Vietnam eSIM, the data connection will not drop thanks to Voice over LTE (VoLTE) on both SIMs. This seamless experience makes dual SIM truly practical for travelers.

Keeping your home SIM active is very useful for receiving banking SMS, ride-hailing app verification codes (Grab, Xanh SM), or two-factor authentication messages. If you’re coming from Korea or Japan, your KakaoTalk or Line registration can stay tied to your home number while the Vietnam eSIM provides data for those apps. To avoid international SMS charges, set Samsung Messages or Google Messages to send via your home line only when needed.

If you require a local Vietnamese phone number for receiving calls (e.g., for hotel check-in or Grab driver contact), we recommend choosing the Vinaphone eSIM plan — it includes a temporary Vietnamese number that can receive incoming calls and SMS. You can also use Samsung’s “Call forwarding” feature to redirect calls from your home SIM to the Vietnam eSIM, but check your home carrier’s roaming rates first. Otherwise, VoIP apps like WhatsApp, Zalo, or FaceTime audio work perfectly over the data connection.

If the eSIM does not activate after scanning the QR code, make sure your phone is connected to Wi-Fi and try restarting the device. Sometimes the profile needs a reboot to connect to the network. If you see “No service” on the eSIM, go to Settings → Connections → Mobile networks → Network operators and manually select “Viettel” or “Vinaphone” depending on your plan. This forces the phone to register on the correct carrier.

APN issues are rare because the Viettel eSIM auto-configures the APN (viettel.vn), and Vinaphone typically sets itself. If you need to enter it manually for Vinaphone, use “m-wap.” For dual SIM problems, ensure both SIMs are activated in the SIM card manager. On some regional firmware, using 5G SA may disable Dual SIM Dual Standby (DSDS) — if that happens, switch the network mode to LTE temporarily. If the eSIM is still not recognized after arriving in Vietnam, delete the eSIM profile, reconnect to Wi-Fi, and scan the QR code again. Your eSIM can be reinstalled as many times as needed before the plan expires.