Modern Xiaomi smartphones give users complete freedom to choose the operator, allowing you to use two numbers at the same time. However, when you first set up or after changing the tariff plan, there is often confusion: which SIM card will be used for outgoing calls and which for mobile traffic. MIUI system and the new HyperOS shell have flexible settings, but not always intuitive at first glance.
The wrong configuration can lead to unpleasant surprises such as debiting funds from an unwanted account or not having access to the network at an important moment. The main SIM card is not just a slot in the tray, but a programmatic priority assignment. In this article, we will detail the process of prioritizing so that you can manage your communications as efficiently as possible.
Consider not only standard methods through the settings menu, but also the nuances of working with 4G/5G networks, as well as possible problems faced by owners of Redmi and Poco smartphones. Proper setting will ensure stable communication and optimize battery consumption, since the modem will know which channel to use in priority.
SIM card management interface in MIUI and HyperOS
The central node of mobile communication management in Xiaomi smartphones is a special section in the system settings. This is where the distribution of roles between the installed roles takes place. SIM-The interface may vary slightly depending on the version of the shell, but the logic of the work remains the same for all current models.
To get to the desired menu, you need to open Settings and select the item SIM-Maps and mobile networks. In some versions of firmware, this section may be called simply Two SIM-Maps and mobile networks. This shows a graphical representation of both slots, indicating the operator and signal level.
At the top of the screen, you'll see switches for each card. Activating the slot allows you to completely disable the second card without physically retrieving it, which is useful in roaming or for saving energy. Below are the default settings for different types of traffic.
⚠️ Note: Changing your network settings may temporarily interrupt your active internet connection. Make sure you have access to Wi-Fi or the second card is ready to take the call if you change the main line settings.
The system allows you to flexibly configure usage scenarios, for example, you can assign one card exclusively for voice and the other card exclusively for packet Internet, an approach often used by those who have connected special tariff plans with a large amount of traffic on one number, while keeping the old number for calls.
Setup the main SIM card for voice calls
The most important aspect for most users is to determine the card from which outgoing calls will be made. By default, the system can request a card selection for each dial, which creates inconvenience. To fix the choice, you need to change the settings in the corresponding menu.
In the section SIM-If you click on the card and mobile network, find Calls or the Main Call Map, and if you click on it, you'll see a list of available carriers, and if you select the SIM card you want, the system will remember that choice for all subsequent actions.
There is also a smart switch feature available in advanced settings that allows you to automatically use a second card to call if the main card is missing or busy, which is critical for business users who can’t risk missing an important contact.
When choosing a primary card for calls, look for indicators next to carrier names. Android highlights an active SIM card with color, which makes navigation easier visually. If you plan to change priorities often, it is more convenient to put the SIM management widget on the desktop.
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For a quick switch of the main SIM card add a widget «SIM-This allows you to change the settings of calls and the Internet in one click without going into the deep settings menu.
Priority of SIM card for mobile Internet
A separate and perhaps the most resource-intensive setting is the choice of a data card, which determines which account will charge money for using instant messengers, browsers and streaming services, and a mistake in this paragraph can cost a lot of money, especially in roaming.
Same menu. SIM-If you want to find the mobile Internet or the Internet, you can select the SIM card that activates the Internet tariff plan, and after you select the system will redirect all traffic through the selected communication module.
It is important to note the work of 4G/5G technology. In most modern Xiaomi smartphones, only one SIM card can work in high-speed data mode, while the second one goes into 2G/3G mode for voice communication. So the choice of the main map for the Internet also determines which number will have access to the high-speed connection.
| Parameter | SIM card 1 | SIM card 2 |
|---|---|---|
| Status | Active. | Active. |
| Operator. | MTS | Tele2 |
| Type of network | 5G/4G (Internet) | 3G/2G (Voice) |
| Priority of calls | No. | Yes (Major) |
If you use unlimited internet rates on certain applications, make sure the main data card matches that operator. Otherwise, when you switch to the mobile network, your favorite services may start spending the main gigabyte package or money from the balance.
Quick SIM card change function when calling
Despite the main card, there are times when you need to make a one-time call from another number. Xiaomi has provided a convenient mechanism for such cases, allowing you to ignore the default system settings for a particular action.
When dialing a phone or calling from contacts, look at the SIM card selection button, which is usually located under or integrated into the call button, and clicking on this button opens a menu where you can choose which SIM card will be used.
In addition, the call settings can activate the "Always Ask" option, which does not rely on a set priority, but instead asks you to select a card before each connection, ideal for those who actively use both numbers equally.
How does switching work at the time of the call?
It is worth remembering that if you are in a bad reception zone, choosing a card for a one-time call can take longer.The system must register with the network of the selected operator before initiate a connection.
Using two SIM cards in 4G and 5G mode
Owners of modern Xiaomi models, such as the Mi 11 series, Xiaomi 13/14 or flagship Poco, are often interested in the possibility of both cards working in high-speed mode.Dual 4G/5G Standby technology allows you to keep both cards registered in fourth and fifth generation networks.
However, the smartphone cannot physically transmit data simultaneously through both cards, the main data card receives a full speed channel, while the second card is in standby mode. If an incoming call arrives on the main card, the second card can temporarily lose connection to LTE/5G if VoLTE is not enabled.
To activate advanced features, go to Settings → Additional (or advanced settings) inside the SIM card menu. There may be a 4G Allow Switch or Network Acceleration switch. Enabling this option allows the second card to also use high-speed networks when the first card is busy talking.
⚠️ Note: Simultaneous operation of two cards in mode 4G/5G If you notice that the Xiaomi smartphone is quickly discharged, try to turn off the second card or put it into mode. 3G/2G.
It’s also worth considering that when using two 5G cards, the internet speed on the main card may be limited by the cooling system and modem capabilities. In most use cases, the speed difference between one active 5G card and two is not noticeable to the user.
Solving problems with determining the main SIM card
Sometimes users are faced with a situation where the settings are confused and the phone stops accessing the Internet or making calls from the selected main card, this can be caused by a software failure of the MIUI shell or a conflict of network settings.
The first step is always to reboot the device, which is a standard procedure that clears the temporary caches of the communication module and makes the phone re-register with updated settings, often solving 90% of the problems.
☑️ Diagnosing problems with SIM-card
If the reboot didn’t work, try resetting your mobile network settings. Go to Settings → Connection & Sharing → Reset Wi-Fi, mobile networks and Bluetooth. Note that this action will remove stored Wi-Fi passwords and paired Bluetooth devices, but return the network settings to factory state.
In rare cases, the problem may lie in the physical contact group: Remove the SIM card tray, wipe the SIM card contacts with soft dry cloth and re-set them. Make sure the card sits tight and doesn't hang around in the slot.
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If after resetting network settings and rebooting the problem with choosing the main SIM card persists, you may need to update the firmware or replace the SIM card itself with a new one from the operator.