Does changing the default data SIM affect calls and texts?

No. The setting under Tap on Settings ➔ Tap on Connections ➔ Tap on SIM card manager ➔ Tap on Mobile data only controls which SIM handles internet traffic. Calls and SMS keep using whichever SIM you have set separately for voice.

Can I use the status bar to switch the data SIM instead of going through Settings?

Yes. The status bar shortcut opens the same SIM card manager and lets you pick SIM 1, SIM 2, or OFF for mobile data without navigating through the full settings menu.

What happens if I set mobile data to OFF for both SIM cards?

Both SIM cards stop using cellular data. Calls and texts still work normally, but apps rely on Wi-Fi only until you select SIM 1 or SIM 2 again in SIM card manager.

Why does my phone keep switching the data SIM on its own?

Some Samsung devices automatically switch the active data SIM when one card loses signal, especially with Dual SIM Always On enabled. Turning that feature off keeps your manual choice in Mobile data fixed.

Samsung

Samsung: Set Default SIM Card for Mobile Data

If mobile data feels slow after inserting a second SIM, your Samsung phone is likely still pulling data through SIM card 1 by default. On some models only that first slot supports fast LTE, so calls or texts on SIM 2 work fine while data stays sluggish. Switching the active data SIM fixes this without removing either card.

Updated: 07.08.20264 min5 steps

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Samsung

Set Default SIM Card for Mobile Data auf Samsung

Samsung phones with dual SIM support assign mobile data to SIM card 1 by default. This happens even if SIM card 2 has a stronger signal or a data-only plan. On several Samsung models, fast LTE is only available on the first SIM slot, so leaving SIM 2 selected for data can mean noticeably slower browsing and downloads.

You control this setting in SIM card manager. Go to Tap on Settings ➔ Tap on Connections ➔ Tap on SIM card manager ➔ Tap on Mobile data, then pick Choose SIM 1 / 2or OFF.

Setting mobile data to OFF disables data on both SIM cards, which is useful when you only need calls and texts or want to force a Wi-Fi-only connection to save your plan. If your phone constantly switches between SIM 1 and SIM 2 for data depending on location, check whether Dual SIM Always On or a similar feature is active, since that can override manual selections.

The same switch is also reachable directly from the status bar shortcut, which is faster if you change SIM cards often, for example when traveling between countries with separate travel and home SIMs.

Frequently asked questions

Several Samsung models only support fast LTE on the first SIM slot. SIM 2 may fall back to a slower network type even when signal strength looks the same, which is a hardware limitation rather than a settings issue.

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Android 11 · One UI 3

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Network & Connectivity

Samsung: Set Default SIM Card for Mobile Data

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