Owners of modern smartphones are often faced with the need to manage several numbers. Two SIM cards in one device allow you to separate work and personal contacts or take advantage of favorable rates from different operators. However, after installing new cards or updating the system, the settings may go wrong, and the phone stops making calls through the desired number or uses the mobile data with the wrong balance.
Changing the default SIM card to Android is quite simple, but the menu location may differ depending on the version of the operating system and the manufacturer's shell. In this article, we will analyze in detail the algorithms of actions for different interfaces, explain the difference between the settings for voice communication and data transfer, and also consider possible errors that interfere with the correct operation of the network.
The correct configuration of these parameters saves battery power and prevents accidental costs for roaming or paid services. Let's take a look at how to regain control over your device's communications and set communication priorities in a way that is convenient for you.
Where to find SIM card management settings
The first step to change settings is to search for the appropriate section in the system menu. In most cases, the path to the necessary settings is through the general device configuration menu. You need to open the application Settings and find the item related to the connection or network.
On pure Android (versions 10 and higher) this section is usually called Network and Internet. Inside it you will see a subsection SIM cards or Mobile network. This is where global switches are stored that are responsible for the behavior of the phone when there are two active communication profiles.
If you use a smartphone with a proprietary shell, for example MIUI from Xiaomi or OneUI from Samsung, names may vary slightly. For Samsung, the required item is often hidden in the section Connections, while for Xiaomi it is placed in a separate menu SIM cards and mobile networks right in the settings root.
⚠️ Attention: If the card control item is inactive (grey), check if the slots themselves are enabled. Sometimes the system disables management if one of the cards is not physically detected or is damaged.
It is important to understand that access to these settings requires device administrator rights, which the owner has by default. However, some corporate profiles or "Guest" modes may restrict access to changing network settings for security purposes.
Setting up a SIM card for mobile calls
The voice card selection feature determines which number will be used to make outgoing calls when dialed from keyboards. This is a critically important parameter, since an incorrect choice can lead to a call from a number that does not have minute packages or is intended only for the Internet.
In the card management menu, find the item Calls or Voice communication. The system will offer three main behavior options: using the first card, using the second card, or asking for a choice before each call. The last option is the most flexible, but requires extra action each time you dial.
If you want to fix the choice, just click on the desired number in the list. After this, all outgoing calls initiated through the standard dialer will go through the selected profile. This is especially convenient if one number is used exclusively for work.
It is worth noting that some instant messengers, such as WhatsApp or Telegram, are tied to a specific number during registration and do not depend on this system setting. They use the Internet channel of the card that is selected for data transfer, but the user identification remains the same.
If you often call different people from different numbers, turn on the “Always ask” function. This will allow you to select the desired SIM card directly in the dialing window before pressing the call button.
Selecting the main card for data transfer
Setting up the Internet is the most important for saving money. Mobile data consumes traffic, and if the phone starts downloading updates or downloading videos through a roaming SIM card, the bill can be impressive.
In the same menu SIM cards find the section mobile data or Data transfer. Here you must explicitly indicate which card provides access to the World Wide Web. The system cannot use the Internet from two cards simultaneously in standard mode.
When changing the main Internet card, the device may lose the connection for a few seconds. This is normal behavior, as the communication module is reconfigured to work with a different network access profile (APN).
| Parameter | Description | Recommendation |
|---|---|---|
| Main data | Card through which all traffic | Choose a card with an unlimited tariff |
| Data roaming | Permission for Internet abroad | Disable when leaving the country |
| Switching | Auto-change when signal is lost | Disable to save battery |
Some advanced users mistakenly believe that they can sum the speed of two channels. With standard equipment, this is impossible without the use of special channel aggregation technologies, which are not supported by all operators and require specific equipment.
⚠️ Attention: Before traveling abroad, be sure to disable data transfer on the second SIM card, unless it is a special tourist tariff. Background processes can activate expensive roaming.
Features of interfaces from different manufacturers
Although the logic of operation Android is the same, the visual implementation of the settings is highly dependent on the manufacturer. This often confuses users switching from one brand to another.
On devices Samsung the settings are separated into different tabs. The choice of SIM card for calls is in the call menu, and the choice for the Internet is in the connection settings. You need to be careful not to change the parameter in the wrong section.
The shell MIUI (Xiaomi, Redmi, POCO) implements a very convenient switch right in the notification shade. A long press on the mobile network icon allows you to quickly change the active SIM card for the Internet without going into deep settings menus.
Hidden settings for advanced users
In the engineering menu (access via code ##4636##), you can see detailed statistics for each card, but changing settings there without understanding the risks is not recommended, as this can lead to loss of the network.
Devices from Google (Pixel) and Motorola offer the cleanest and most logical interface. Here, all parameters are collected in one screen, and switching occurs instantly with clear color-coding icons for each card.
☑️ Checking settings after update
What to do if the settings are not saved
Sometimes users are faced with a situation where, after rebooting, the phone resets the default SIM card selection to another or to the request. This may be caused by a software glitch or a profile conflict.
First, try removing both cards and reinserting them, making sure they fit tightly in the slots. Poor contact can lead to the system periodically “losing” one of the cards and resetting the settings to the remaining working one.
If physical reconnection does not help, clear the application cache Phone and Settings. To do this, go to Applications, find the desired system application, select Storage and press Clear cache. Do not confuse this with data clearing, which will delete your personal settings.
⚠️ Attention: On some models with a hybrid slot (SIM + microSD), installing a memory card may block the second SIM card slot. Make sure that you really have two active SIM cards, and not one SIM card and one flash drive.
In rare cases, the problem lies in an outdated version of the basic modems. Check for system updates in the About the phonesection. Manufacturers often release patches that correct errors in working with operator networks.
Using quick settings and widgets
To quickly change priorities, it is not necessary to go deep into the menu every time. Modern versions Android allow you to move the SIM card switcher to the quick settings panel.
Swipe down from the top edge of the screen twice to reveal the full panel of tiles. Find the mobile network icon or the special SIM card tile. If it is not there, click on the pencil (edit) and drag the desired switch to the active zone.
This is especially useful when temporarily using a second card. For example, if you urgently need to send a message from a work number, but the default is personal, you can do this with two touches of the screen.
Quick access to switching SIM cards through the notification shade saves time and reduces the risk of errors when choosing a number for an important call.
There are also third-party widgets and launcher applications that allow you to create scenarios. For example, automatic switching to a specific SIM card when launching a specific application or at a given time of day, although such automation is difficult to implement using standard system tools.
Frequently asked questions
Is it possible to receive calls on both SIM cards at the same time?
Yes, standby mode is active for both cards, regardless of the software settings default. The default settings apply only to outgoing actions (calls, SMS, Internet). Incoming calls will be sent to both numbers if the cards are active and there is a network signal.
Does the choice of SIM card for the Internet affect the connection speed?
The speed depends solely on the operator’s tariff, network coverage in your area and the load on the tower, and not on the system settings of the phone. However, if you choose a card with a poor signal as the main one for data, the speed will be low.
Why does the phone itself switch the Internet to another SIM card?
This can happen if the Smart Switch function is enabled. It activates the second card if the signal on the main one is lost. Disable this option in the SIM card settings to fix the choice.
How to send an SMS from another SIM card without changing the settings?
In the messages application, when creating a new letter, there is usually a SIM card icon next to the number entry field or the send button. Click on it to select the sender for a specific message.
Are settings reset when changing the region on the phone?
Usually no, but with a full factory reset, all SIM card priorities will be reset, and the phone will ask you which card to use for calls and the Internet when it first boots.