Your travel eSIM is installed at the overseas airport. Can you stop worrying about your home line’s charges? Adding an eSIM and choosing which line supplies data are separate tasks. Carrying two passports would not tell an immigration counter which one you intend to use.
Apple guidance checked on October 19, 2026. This article covers Dual SIM on supported iPhones; do not apply these menus directly to Android. Check charges with your carrier for your plan and destination.
Key points
- Installing a travel eSIM and choosing the data line require separate checks.
- Review the Korean number, data roaming and call or text charges for each line.
- After returning, verify the home line and data setting rather than assuming an automatic switch.
Four checks after installation
Read the roles of the two lines separately.
- 01CompatibilityModel, purchase region and carrier lock
- 02Data lineConfirm the travel line selection
- 03Roaming and chargesSettings and plan terms for each line
- 04Back homeRecheck the Korean line and data
1. Must you remove the Korean SIM first?
Supported models can use a physical SIM and an eSIM together, so removing the physical SIM is not automatically necessary. To use a travel eSIM from another carrier, the iPhone must not be locked to a carrier. In Settings → General → About, check Carrier Lock for “No SIM restrictions,” and verify eSIM support for the model and purchase region. Apple travel guidance
Give the lines recognizable labels such as “Korean number” and “Travel data.” These are editorial examples, not actual plan names.
2. Default voice and data are different selections
In Settings → Cellular → Cellular Data, check that the travel line is selected for internet access. You can choose voice and data lines separately; an iPhone uses one cellular data network at a time. Do not assume your calling and messaging number has also changed to the travel line. Dual SIM guidance
| Setting | What it means | Check before departure or on arrival |
|---|---|---|
| Turn On This Line | Whether that line is active | Decide whether to keep the Korean number active |
| Cellular Data | Line used for internet access | Confirm the travel line is selected |
| Data Roaming | Overseas data setting for each line | Follow each plan’s instructions |
| Default Voice Line | Default calling and messaging number | Check the outgoing number and carrier charges |
3. Should you turn all roaming off?
If you do not intend to use data roaming on the Korean line, select that line and check its roaming setting. Follow your travel provider’s instructions for the travel line. Checking one line’s screen does not configure both lines. Menu names and locations may vary with iOS version and carrier. Data roaming guidance
Apple warns that a home line left on may still incur roaming charges even when the travel eSIM is used for data. A data setting does not make every call and text free. Ask the home carrier about charges if you plan to call or text using the Korean number. Do not assume a data-only plan includes a local phone number or conventional calls. Travel plans and charges
4. Check the lines before deleting anything after returning
With iOS 26 or later, depending on country or region, the travel line may turn off automatically and the home SIM may turn back on. If there is no notification, check that your Korean line is active. Also check that cellular data has returned to the usual line, and turn off travel lines no longer needed. Do not assume automatic switching occurs on every device. After returning home
Before departure, check support, locks and plan conditions. On arrival, check the data line and each line’s roaming setting. After returning, check the Korean line again. The final question is less “Is installation complete?” and more “Which line is doing which job?”