How to set up a second line on a Xiaomi phone: a complete guide with pictures and life hacks

Have you bought a new Xiaomi with two SIM- cards, but don’t know how to set up the second line correctly? Or have you been using a smartphone for a long time, but the second slot is idle? In this article, we will analyze all the nuances from the physical installation of the card to fine-tuning calls, the Internet and notifications. We tested the instructions on the Redmi Note 12 Pro+, POCO X5 Pro and Xiaomi 13 Lite — it works on all models with a Hybrid slot (combined with nanoSIM + microSD) and Dual-SIM (two separate slots).

We'll focus on the typical issues of why the second SIM doesn't catch the network, how to split traffic between the cards, and what to do if the phone doesn't see the new SIM, and at the end, a unique life hack for those who want to use one SIM for calls and the second one for mobile Internet only without unnecessary notifications.

1. Compatibility Check: What is the second SIM slot in your Xiaomi?

Before you buy a second SIM- card, make sure your Xiaomi supports Dual-SIM at all. Even if the box says "2 SIM," it doesn't always mean two physical slots. Here's how to check:

• 🔍 Hybrid slot (most common): one slot for nanoSIM + microSD, the second slot only for nanoSIM. Example: Redmi Note 11, POCO M4 Pro.
• 📱 Dual-SIM (two separate slots): both slots are only nanoSIM, no memory card support. Found in flagships: Xiaomi 13 Ultra, Mix Fold 2.
• ⚠️ One slot: If you have a Xiaomi 12S Ultra or Black Shark 5, the second SIM is not physically supported.

To determine the type of slot:

1. Take a paper clip and carefully remove the tray for the SIM- card (usually it is on the left end of the phone).
2. Count the number of connectors: 2 connectors – Dual-SIM (you can insert two nanoSIMs). 3 connectors – Hybrid (two nanoSIM or one nanoSIM + microSD).

⚠️ Warning: If you're using a Hybrid slot and you've inserted a microSD, the second SIM- card won't work! You'll have to choose between a second SIM or a memory extension.

2 Installation of the second SIM- card: step-by-step instructions with photo

Now, let's get to the practice. You're going to need to:

• 📱 Xiaomi smartphone with Dual-SIM support.
• 🪪 Second nanoSIM card (if you have a Hybrid slot, make sure it's not microSIM or miniSIM).
• 📎 A paper clip or special key to extract the tray (goes with the phone).

Installation steps:

If the second SIM is not determined after the switch is turned on:

1. Reboot the phone.
2. Check if the card is inserted correctly (the chip should be directed downwards, the beveled corner should be directed to the phone body).
3. If you have a Hybrid slot, make sure that it doesn’t have a microSD.
4. Try inserting the SIM into another slot (sometimes the first slot is more stable).

3 Priority Setup SIM- Cards for Calls and SMS

By default, Xiaomi offers you to choose which SIM to use for calls and messages. But what if you want outgoing calls to come from one card and SMS from another? Or if the second SIM is only for the Internet? Here's how to set it up:

Open Settings → SIM- Maps and Mobile Networks and select:

• 📞 Calls: press CIM for calls and select the main card, and you can turn on the "Ask Always" option, so that every time you call, the phone will ask you to select SIM.
• 💬 SMS: similarly configure "SIM for SMS." Note that if you select "Ask Always," you will need to manually specify the map when sending the message.
• 🌐 Mobile Internet: Choose which SIM will be used for data transfer. If you want the Internet to only work over Wi-Fi, turn off mobile traffic for both cards.

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If you travel frequently, set up roaming for only one SIM to avoid unexpected expenses. To do this, go to Settings → SIM- Cards → [select SIM] → Roaming and turn off the unnecessary option.]

For advanced users: If you need a second SIM to be internet-only (no calls and no SMS), follow the following steps:

1. Open Settings → Applications → Application Management.
2. Find the Phone app and click on Permissions.
3. Turn off permission to access the second SIM.
4. Repeat the same for the Messages app.

The second SIM will now be used only for mobile internet, and calls and SMS will go through the first card.

4.Separating Mobile Traffic: How to Get Apps to Use the Right SIM

One of the most common problems with using two SIMs is that you have uncontrolled traffic consumption, like WhatsApp can eat the Internet from the first SIM, and you need it to work through the second.

The MIUI 14 and HyperOS have a feature for associating applications to a specific SIM- card.

1. Go to Settings → SIM- Cards and Mobile Networks → Applications Link to SIM- Card.
2. Select an app from a list (such as Telegram or YouTube).
3. Specify which SIM it should use for the internet.

If this option is not available (on older versions of MIUI), you can go a workaround:

• 📵 Disable mobile traffic for the first SIM in Settings → SIM-maps → [Select SIM] → Mobile traffic.
• 🔄 Enable traffic only for the second SIM.
• 🔒 Set a traffic limit for each SIM to avoid overspending: Settings → SIM-cards → [Select SIM] → Traffic limit.

5. Optimizing the operation of two SIMs: the balance between battery and communication

Two active SIM- cards increase battery consumption by 10-15%, because the phone is constantly scanning the networks of two carriers. To save charge, use these tips:

• 🔋 Turn off network search for the second SIM if it is rarely used: Settings → SIM- maps → [Select SIM] → Enable this SIM- card (switch to off position).
• 📶 Set 2G for the second SIM if it is only needed for calls: Settings → SIM-cards → [Select SIM] → Preferred network type → 2G.
• ⚡ Enable the Power Saving Mode for the Background: Settings → Battery → Power Saving Mode → Enable for background tasks.

Also, check out the VoLTE (Foundation over 4G) settings, and if your carrier supports this technology, turn it on for both SIMs:

1. Go to Settings → SIM- Cards and Mobile Networks → [select SIM] → Enable VoLTE].
2. If the option is not available, update the firmware or contact the operator for activation.

⚠️ Warning: Some Xiaomi models (e.g., Redmi 9A or POCO M3) may disable 5G support when two SIM are active. If you care about top internet speed, use only one SIM or check your network settings manually.

6. Solving common problems with the second SIM

Even after setting up the second SIM correctly, it can malfunction, and we've collected the most common problems and solutions:

Problem 1: The second SIM is not registered on the network

If the phone sees the card, but it doesn't catch the network:

• 🔄 Reboot the phone.
• 📶 Manually select operator: Settings → SIM- maps → [select SIM] → Network operators → Manual search.
• 🪪 Check if SIM is blocked by the operator (call from another phone to that number).
• 🔧 Reset network settings: Settings → SIM-maps and mobile networks → Resetting mobile network settings.

Problem 2: Application binding to SIM is permanently reset

This is a MIUI bug that occurs after the updates.

1. Clear the cache of the Settings app: Settings → Apps → App management → Settings → Clear the cache.
2. If it doesn’t help, reset your network settings (see above).

Problem 3: SMS does not come to the second SIM

Possible causes:

• 📵 The SMS- Message Center is lost. Check the correct number with the operator and enter it into Settings → SIM- Maps → [Select SIM] → Message Center.
• 🚫 Lock SMS from unknown senders: Settings → Applications → Messages → Lock and filter.
• 🔄 Reinstall the Messages app via Google Play.

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If the second SIM stopped working after the firmware update, try to roll back on the previous version of MIUI or wait for a patch from Xiaomi.

7 Hidden Chips: How to Use Two SIMs as Effectively as Possible

Few people know, but Xiaomi has a few hidden features to work with two SIM- cards.

• 🔄 Quick switch between SIM: double click on the network icon in the notification bar – the SIM selection menu for calls will open.
• 📞 Different tunes for different SIM: in Settings → Sounds and Vibration → Calling Sound SIM- cards can be assigned unique ringtones.
• 📊 Traffic statistics on SIM: Settings → SIM-maps and mobile networks → Traffic usage – you can see how much internet each card spent.
• 🔒 Prohibit outgoing calls: If you give a phone to a child, you can block outgoing calls for one of SIM: Settings → SIM- cards → [Select SIM] → Outgoing calls → Prohibit.

And now, a unique life hack for travelers: if you often travel abroad, set the second SIM as “local” (for example, buying a local SIM in roaming), and leave the first one to receive calls to a Russian number, so as not to pay for incoming roaming:

1. Turn off incoming calls for the first SIM: Settings → SIM- cards → [select SIM] → Incoming calls → Reject all.]
2. Enable redirect to the second SIM: dial USSD- command 21 [second SIM]# number and press Call.]
3. All calls to the first SIM will be automatically redirected to the second SIM without any additional roaming costs!

FAQ: Frequent questions about the second SIM in Xiaomi