Modern Xiaomi smartphones, which are based on the MIUI shell or the new HyperOS, are initially focused on working with two SIM cards, which allows users to flexibly manage personal and work contacts. However, after first installing new chips or resetting settings, the system may not know which card to use for outbound calls or mobile Internet access, which causes confusion among owners.
Setting communication priorities correctly is not just a matter of convenience, but also a way to save on tariffs if you have different conditions for calls and traffic. In this guide, we will detail how to force the default SIM card on Xiaomi, change settings for individual applications, and solve typical networking problems.
The setup process takes only a few minutes, but requires care, as the menu interface may vary slightly depending on the version of the operating system. We will look at the algorithms for current versions of firmware, so you can be sure of the stability of the connection.
Double settings SIM-map
The first step to make the device work properly is to log into the dedicated map management menu. You need to go to Settings, select a point. SIM-Maps and mobile networks (sometimes referred to as just two) SIM-This is where the global settings that determine the behavior of the smartphone when interacting with the operators are located.
In the window that opens, you will see switches for each card you install, allowing you to activate or deactivate them, and change the network name for easy identification. A key element of this section is the default settings block, where the system requests the choice of the main card for various types of communication.
Note that if you just inserted SIM cards, the system can automatically suggest that you configure them, but manual control is always more reliable. Here you can configure the display of network icons in the status bar, which is especially useful when using cards from different operators with different coverage.
- 📱 Card 1 and Map 2: The main slot activity switches.
- 📞 Calls: Select the number from which the default dial will go.
- 💾 Mobile Internet: Identifying a Priority Channel for Data Transmission.
- 💬 SMS: map assignment for sending text messages.
⚠️ Note: If you change your mobile internet settings, the active data session will be interrupted and the downloads that are running may stop, so complete important operations before switching.
Selecting the main card for calls and messages
To install the default SIM card on Xiaomi in the context of voice communication, look in the control menu for Calls. Click on it, you will see a list of available SIM cards and the option Always ask. Selecting a specific operator means that when dialing through a standard contact list or call history, the connection will be established automatically over the selected network without unnecessary confirmation.
The same is true of text messages. In SMS, you set a priority card for outgoing correspondence. This is convenient when you have a tariff with unlimited SMS or a packet of minutes that you want to use first. However, if you often communicate with different contact groups, Always Ask can be a more flexible solution, allowing you to choose the number directly at the time of sending.
It is important to understand the difference between default settings and one-time choices. By prioritizing, you speed up the dialing process, but you lose the ability to instantly control if you forget about the changes you make. Therefore, the Always Ask mode is recommended for users who actively balance costs between the two operators to avoid random spending on a more expensive card.
☑️ Checking the communication settings
Priority of mobile data (4G/5G)
The most critical parameter for most users is the choice of a card for the mobile Internet. In the section Mobile Internet or Data Transfer, you must specify the SIM card through which you will connect to the network. It should be remembered that in most models Xiaomi high-speed Internet (4G/LTE/5G) It can work on only one card at a time, the second will work on the same card. 2G/3G voice-over.
If you switch the Internet priority from one card to another, the system automatically reconfigures the modem, at which point the network icon at the top of the screen may disappear for a second or change the 4G/LTE indicator to H+ or G on the second card, this is the standard behavior of the equipment, indicating the reallocation of antenna resources.
For users who want to have constant access to the network from both cards, some modern models offer the function of Accelerate games or special modes that allow you to use the channels of both SIM cards at the same time, but this requires support from the operator and a particular smartphone model.
| Parameter | Description of function | Impact on the battery |
|---|---|---|
| Calls (SIM 1) | Automatic dialing through the first operator | Minimum |
| Internet (SIM 2) | Using Second Card Traffic for All Applications | Medium (working 4G modem) |
| Always ask | Requesting a card selection before each action | Low. |
| Data roaming | Allowing data transfers in other networks | High (network search) |
Individual settings for applications and contacts
The MIUI shell provides advanced management capabilities that go beyond global settings. You can assign a specific SIM card to a specific contact or application. For example, for instant messengers like WhatsApp or Telegram that are linked to a phone number when you sign up, it matters which card is active when you receive the confirmation code, even though they work through any available Internet later.
Moreover, the phone’s settings often feature “Use for,” where you can detail the rules, such as setting up a scenario where calls to certain numbers always go through a second SIM card, regardless of the global default setting, implemented through smart rules or third-party phone apps compatible with Xiaomi’s system.
Also worth mentioning is the ability to customize the display of the subscriber name. If you use two cards of the same operator or cards of different operators with similar numbers, properly configuring the names in contacts and linking them to specific SIM cards will help avoid awkward situations when calling.
- 📞 Contacts: Selecting the default number for each contact separately.
- 📱 Applications: Linking services to a specific number for authorization.
- 🌐 Guest mode: restriction of access to the data of the second card.
⚠️ Note: When you change the main card for the Internet, applications using VoIP (network calls) can briefly lose the connection or switch to Wi-Fi if it is not stable.
Secret codes for checking SIM
Solving problems with the definition of SIM cards
Sometimes users are faced with a situation where after installing the default SIM card on Xiaomi, the phone stops seeing the network or shows the status of “No service”. Often the problem lies in the incorrectly cropped sim-cards of the Nano-SIM format, which can get stuck in the tray or not reach the contacts, in such cases, it is recommended to remove the tray and check the density of the chip.
Another common cause of failure is frequency conflict or outdated network settings. If one of the cards stopped catching the signal after changing the settings, try resetting the network to factory settings. This action will not delete your personal data (photos, contacts), but return the original modem parameters, which often solves the problem of sticking the network on one standard.
It’s also worth checking if the backdoor limiting feature for phone-related apps is activated. In newer versions of HyperOS, aggressive battery optimization can block the second SIM card from working in the background, making it unavailable for incoming calls until you open the Phone app.
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If after changing the settings, the Internet did not work, try to turn on the flight mode for 10 seconds, and then turn it off - this will forcibly restart the communication modules and re-register the device in the operator's network.
Additional capabilities and cost management
Xiaomi’s system includes built-in traffic and spending monitoring tools that are closely related to SIM card settings. The Security or Services app allows you to set traffic limits for each card separately, allowing you to tightly control which SIM card is used for heavy content and which remains backup for emergency communication.
Traffic Saving can be customized for each SIM card, and by activating it for a limited-pack card, you can prevent background apps from using up its resources by redirecting all activity to an unlimited-rate card or Wi-Fi network, an effective way to extend the life of an expensive plan.
Don’t forget to switch quickly. By adding a SIM management widget to your desktop or notification curtain (via dashboard editing), you can change your calls and Internet priorities in one click without diving deep into the settings menu each time.
- 📊 Statistics: viewing the consumption of minutes and gigabytes for each card.
- 🚫 Blocking: Banning background data transmission to save money.
- ⚡ Widgets: Quick access to SIM card management.
⚠️ Note: When you turn off data in the background for the main SIM card, notifications from messengers may come with a delay until you open the application.
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Competent separation of functions between SIM cards (for example, calls on one, the Internet on another) allows you to significantly save your budget and extend the battery life of the smartphone.