Set up Dual SIM with a regular SIM and travel eSIM

Set up Dual SIM for travel as follows: use your regular SIM for calls and texts, select the HolySim eSIM for mobile data, enable roaming on HolySim, and disable it on your regular line. Turn off automatic mobile data switching if you want to prevent unexpected carrier charges.

HolySim advice: first give both lines a clear name. Most configuration mistakes happen because two generic carrier names look alike.

Which combinations are possible

Dual SIM can consist of a physical SIM and eSIM or two active eSIMs. The permitted combination depends on the phone model, sales region, software, and carrier.

The basic setup is always the same:

• both desired lines are enabled;
• one line is the default for calls;
• one line is the default for SMS or messaging;
• one line provides mobile data;
• roaming is configured deliberately for each line.

Check the exact device in the HolySim device checker before buying a second profile.

The recommended setup for travel

Keep your regular number active for verification codes and calls. Use HolySim only for data if the plan does not include a phone number.

Configure the lines as follows:

1. Name your regular SIM My number.
2. Name the new eSIM HolySim travel.
3. Select My number for calls.
4. Select My number for texts.
5. Select HolySim travel for mobile data.
6. Enable roaming on HolySim travel.
7. Disable roaming on My number.
8. Turn off automatic data switching.

WhatsApp normally remains linked to your existing number. You do not need to change the account when only the internet connection runs through the eSIM.

Set up Dual SIM on iPhone

Open Settings > Cellular. Tap each line to check the label and enable or disable the line. Then select:

• your regular number under Default Voice Line;
• HolySim under Cellular Data;
• turn off Allow Cellular Data Switching;
• enable Data Roaming under the HolySim line.

You can save a preferred line for each contact. Otherwise, iPhone uses the default line or the line you last used to call that contact. Apple explains this behavior under using Dual SIM with an eSIM.

An iPhone uses one mobile data network at a time. Two visible lines therefore do not mean that both plans consume data simultaneously, unless data switching or a specific calling feature uses the other line.

Set up Dual SIM on Samsung

Open Settings > Connections > SIM manager. Enable both lines and use Preferred SIMs to assign calls, messages, and mobile data.

Select HolySim for mobile data. Then go to Connections > Mobile networks and check Data roaming. Some One UI versions manage roaming together with the selected data line. Check the active data line once more before enabling roaming.

The option to always ask when making calls can be useful for work and personal lines, but it is less safe when traveling if the travel eSIM is data-only. In that case, select your regular SIM as the fixed voice line.

Set up Dual SIM on Google Pixel

Go to Settings > Network & internet > SIMs. Tap each SIM to enable it and choose its preferences. Set HolySim for mobile data and your regular SIM for calls and texts.

Pixel may offer Ask every time for calls. For texts, select a default line or choose the line in the messaging app. Options during simultaneous calls vary by Pixel generation and carrier; Google describes these exceptions in the Pixel Dual SIM guide.

Prevent unexpected charges

Dual SIM does not prevent roaming charges by itself. Your regular line can still receive calls, forward voicemail, or handle text and call traffic according to your carrier's rates.

Before departure:

• check the call and text rates of your regular carrier;
• disable mobile data and data roaming on the regular line;
• turn off Wi-Fi Assist or automatic data switching;
• use internet calling over HolySim data where this is legally and technically possible;
• leave unknown incoming calls unanswered if receiving them costs money.

Receiving texts is free with many carriers, but this is not a universal rule. Check your own plan.

Test which line is using data

Turn off Wi-Fi and open a website. Then check data usage by SIM to see whether the HolySim line registers traffic. You can also temporarily disable the regular SIM for a short test. Enable it again afterward if you want to remain reachable.

If the internet does not work, first check the active data line and roaming. Then verify the APN and network connection without deleting a profile.

Sources and editorial review

The settings were checked against Dual SIM documentation from Apple, Samsung, and Google. Names and simultaneous features vary by model, region, software, and carrier. Charges for calls, texts, voicemail, and roaming come from your regular plan and must be checked there. Last editorial review: July 15, 2026.