Setting up SIM- default card for SMS on Xiaomi: the complete guide

Modern Xiaomi smartphones support dual SIM- cards, but many users face a problem: default messages are sent from the wrong card they want to use. This is especially true for owners of hybrid slot devices, where the second SIM shares space with the memory card. In this article, we will discuss how to properly configure the SIM- default card for the SMS on Xiaomi smartphones (including the Redmi, POCO and Black Shark models), avoiding typical errors.

The problem of choosing SIM for messages is complicated by the fact that MIUI (Xiaomi firmware) has several levels of settings: general system parameters, Messages application settings, and even separate options for specific contacts. In addition, after updating the firmware or resetting the settings, SIM priority can be lost. We will take a detailed look at all configuration methods, including hidden functions that are not written in the official instructions.

Why it is important to set up the SIM- card by default for the SMS

Many users underestimate the importance of setting up SIM correctly for messages until they face the consequences.

• 💰 Rate plans: If you have different rates on SIM- cards (e.g. unlimited SMS on one and paid on the other), making the wrong choice will lead to unexpected costs.
• 📡 Coverage area: One of the SIM can better catch the network in your region, and messages will leave through the second, where the signal is weaker.
• 🔒 Security: Some banks and services link SMS- notifications to a specific number, and if the message leaves with another SIM, you will not receive a confirmation code.
• 🌍 Roaming: On trips, an incorrect SIM can cause a shipment block or high fares.

For example, if you use Tele2 for the Internet and MTS for calls/SMS, but Tele2 is chosen by default, then all messages will go through it - even if you have unlimited SMS on MTS. This is a situation where users lose money due to incorrect settings.

How to change the SIM- card by default in MIUI

In MIUI firmware (versions 12-15), there are three main ways to prioritize SIM for messages, and let’s look at each with nuances in mind.

1. Through the main system settings

This is the most obvious, but not always the most reliable, method.

1. Open the Settings. → SIM-maps and mobile networks.
2. Select the SIM- card by default (in some versions of the MIUI, it may be called SIM Priority).
3. Click on Messages and specify the desired SIM- card (1 slot or 2 slot).

⚠️ Attention: In MIUI 14+, this item may not be available if you have only one SIM- card installed or you use an eSIM.

2. Through the "Messages" app

The settings inside the messenger take precedence over the system settings. To change the SIM:

1. Open the Messages app (the envelope icon).
2. Slip on three dots in the upper right corner and select Settings.
3. Go to Additional Settings → SIM- card for SMS.
4. Select the slot you want (e.g. SIM 1 (MTS)).

If this item is missing, your version of MIUI uses system settings (method 1). Also check if you have a third-party SMS application (e.g. Google Messages) that may have different settings.

3. For a specific contact

You can set an individual SIM- card to send messages to a particular subscriber:

1. Open the chat with the contact in the Messages app.
2. Click on the contact name at the top of the screen.
3. Select the SIM- card by default and specify the desired one.

This is useful if you are communicating from one number and your personal correspondence from another, but this does not affect system settings and only works within the Message application.

Make sure both SIM- cards are active in Settings → SIM- cards

Check the priority in Settings → SIM- cards by default

Open Messages → Settings → SIM- Card for SMS

Send the test SMS to your second number for verification-->

Common Mistakes and How to Avoid Them

Even after setting up the SIM default, users are faced with problems, and here are the most common errors and their solutions:

Pay special attention to situations where the application requests SIM selection every time it sends, which means that the settings have "Always Ask" mode on, to turn it off:

1. Open Messages → Settings → More.
2. Find the Ask Always item and turn it off.
3. Please specify the default SIM in the same menu.

Features for different versions of MIUI

The interface and settings may vary depending on the firmware version, and here are the key differences:

MIUI 12 and below

In older versions, the path to SIM settings for SMS looks like this:

Settings → Additional → SIM-cards by default → Messages

There could also be a separate SMS- center, which would have the operator's message center number, and in the newer versions, that's hidden.

MIUI 13–14

Starting with the MIUI 13, settings have been simplified but added duplicate options. Now, the priority of SIM for the SMS can be set to:

• 📱 In Settings → SIM-maps and mobile networks → SIM-maps by default.
• 💬 In the Messages app itself (the path described above).

If the settings conflict, the “Messages” application takes priority.

MIUI 15 (HyperOS)

In the new HyperOS shell (which replaced MIUI in 2026), the logic has remained, but the interface has changed.

Settings → Connections → SIM- Cards → Settings SIM → Messages

HyperOS also allows you to link SIM to specific types of messages (for example, separately for SMS and MMS).

Settings → Applications → Application Management → Messages → Clear the cache

How to check which SIM is leaving the SMS

To make sure that messages are sent from the correct SIM- card, follow the following steps:

1. Send the test SMS to another number (for example, from Telegram or WhatsApp on your computer).
2. Look at which number the message came from, and if it's not the number you chose, then the settings didn't apply.
3. Check the log of sent messages in the Messages app – next to the message should be displayed the icon SIM- of the card from which it was sent.

⚠️ Warning: Some carriers (e.g. Yota or virtual carriers like Tinkoff Mobile) may mask the sender number, in which case check the settings in the operator's personal account - possibly the Hide Number option is enabled there.

If the test message doesn’t reach or leaves the wrong SIM, try:

• 🔄 Reboot the phone.
• 📶 Temporarily disable mobile internet (on some firmware, this interferes with sending SMS).
• 🔧 Reset network settings to Settings → SIM- maps → Reset mobile network settings.

Additional settings for experienced users

If standard methods do not help, you can use hidden MIUI functions or third-party tools.

1.Use of USSD-team

Some operators allow you to manage services through USSD- commands, for example, to check balance or change the tariff. However, you can not change SIM for SMS via USSD through USSD. But you can check whether your SIM is active by sending:

• For MTS: *100#
• For Beeline: *102#
• For MegaFon: *105#
• For Tele2: *107#

2. Configure through Engineering Mode (for advanced)

⚠️ Warning: This method requires caution and is only suitable for advanced users. Misconduct can disrupt the communication module.

To open the engineering menu:

1. Please dial the phone application ##4636##.
2. Select Phone Information.
3. Scroll down to the SIM Information block.

Here you will see detailed information about each SIM, including the SMS Center Number. If the SMS- Center number is empty or incorrect, no messages will be sent.

1. Check the correct number of the SMS-center with your operator (for example, for MTS it is +79169997766).
2. In the engineering menu, select the desired SIM and enter the number in the SMSC field.
3. Save the changes and restart the phone.

💡

If you stop sending messages after changing the SMS- center, return the standard value or contact the operator for support. The wrong SMSC number is one of the most common causes of problems with SMS.

3. Third-party applications for SIM management

Google Play has apps that allow you to flexibly manage SIM- cards, such as:

• 📲 Dual SIM Selector – allows you to quickly switch between SIM when calling and SMS.
• 📲 SIM Toolkit – shows hidden operator settings (if supported).

However, be careful: many of these apps require permission to send SMS, which may not be safe.

Frequent questions and answers