Why Xiaomi shuts down the Internet when calling: a full analysis of the problem

Have you noticed that your Xiaomi smartphone suddenly loses mobile Internet when you call in or out? This problem is familiar to many users of the brand, from budget Redmi to flagship Mi and POCO. At one point you are talking on the phone, and at the same time you can not load a page in the browser, receive a message in the messenger or update maps in the navigator. Why is this happening and how to fix it?

There are many reasons, from the nature of the network. 2G/3G/4G to incorrect VoLTE settings (voice through the LTE) In this article, we will look at all possible scenarios, including the rare cases where the problem lies in the firmware or the hardware limitations of a particular model. SIM-You'll learn how to diagnose a malfunction and restore a stable Internet during conversations without losing quality.

Important: The solutions will be relevant for all modern Xiaomi devices, including the Redmi Note 12/13, POCO X5/F5, Xiaomi 13/14 and older models based on MIUI 12-14. If your phone is released before 2018, some methods may not work – we will mention this too.

1.Why the Internet is turned off when you call: technical reasons

Before we get to the settings, let's get to the root of the problem: Most of the time, when you're on a call, you're disconnecting the Internet from the way your phone switches between the voice and the communication channels, and here are some key technical points:

• 📶 Lack of VoLTE support: If your Xiaomi doesn't support voice over technology 4G (Voice over LTE), When he calls, he has to switch to the network. 2G/3G, Where the Internet is slower or shut down altogether.
• 🔄 Incorrect network settings: Manually selected mode Only 3G or 4G It can interfere with voice calls, especially if the operator has not optimized the network for such cases.
• 📱 Chipset Limits: Cheap Xiaomi models (e.g. Redmi) 9A or POCO C31) They often use budget modems that are physically unable to support voice and data on older networks at the same time. 4G.
• 🔌 Problems with SIM-Map: Old or damaged SIM-The cards may not support modern protocols, which is why the phone “resets” the Internet when calling.

Interesting fact: in countries with developed infrastructure (for example, in South Korea or Japan), the problem is less common, since operators have widely implemented VoLTE and 5G SA. In Russia and the CIS, many providers still use hybrid networks, where voice and data are separated through different channels.

2. VoLTE is the main culprit or solution?

VoLTE (Voice over LTE) technology allows voice calls to be transmitted over a 4G network without interrupting the Internet connection. If it is disabled or not supported, the phone falls on 2G/3G when calling, where data speed is limited or absent at all.

How to check if VoLTE is enabled on your Xiaomi:

1. Open the Settings. → SIM-maps and mobile networks.
2. Choose yours. SIM-map.
3. Find the VoLTE option (sometimes hidden in Additional Settings).
4. Make sure the switch is active.

If VoLTE is not on the menu, it can mean:

• 🛠️ Your Xiaomi model doesn’t support VoLTE (relevant to devices until 2019).
• 📡 Your operator does not provide VoLTE service for your tariff or region.
• 🔄 Firmware update is required (in some cases, VoLTE is activated after the update).

Important: Even if VoLTE is turned on, but the Internet still shuts down, the problem may be in the APN settings or conflict with Dual SIM.

3.APN settings and Dual SIM conflicts

Incorrect APN (Access Point Name) settings are one of the most common causes of Internet problems during calls, and if the APN is set up incorrectly, the phone can "lose" data when switching between voice and the Internet.

How to check and reset your APN settings:

1. Go to Settings. → SIM-maps and mobile networks → [Yours. SIM] → Access points (APN).
2. Click on the three dots in the top right corner and select Reset to default values.
3. If the reset did not help, manually create a new APN with the parameters of your operator (they can be found on the official website of MTS, Beeline, etc.).

For Xiaomi users with two SIM-cards (Dual) SIM) problem may be complicated:

• 🔀 If one of them SIM It is used only for calls, and the second for the Internet, when calling from the "voice» SIM The phone can turn off the data on the second card.
• 📵 Some Xiaomi models, for example, POCO X3 Pro) have hardware limitations: when an active call is made on one SIM second-hand.

Critical information: On some MIUI firmware, an APN reset may result in the loss of MMS. Before changing your settings, save the current configuration (take a screen picture).

4.Firmware problems and regional restrictions

If you use Xiaomi with global (Global), Chinese (China) or custom firmware, the internet problem when calling can be related to:

• 🌍 Regional restrictions: Chinese firmware often lacks VoLTE support for Russian operators.
• 🔧 bagami MIUI: In some versions (e.g, MIUI 12.5 for Redmi Note 10) errors with switching networks were recorded.
• 🛠️ Unofficial firmware: Castom builds (e.g. LineageOS) may not work properly with the modem.

How to check the firmware version and region:

1. Open the Settings. → The phone.
2. Find the MIUI version and the Region.
3. If the region is listed as China and you use a Russian SIM, that could be the cause of the problem.

Decisions:

• 🔄 Update your firmware to the latest stable version via Settings → Updating the system.
• 🌐 If you have Chinese firmware, consider reflashing to Global or EEA (European.
• 📡 In the end, go back to the older version. MIUI, where the problem is not observed (relevant to Redmi 9 and POCO M3).

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Before flashing backup, back up your data through Settings → Additional → Backup and Reset. This will save you from losing contacts and photos.

5. Hardware limitations and modem problems

If the software methods did not help, the problem may lie in the "hardware":

How to check the hardware serviceability:

1. Try inserting. SIM-If the problem is repeated, it is the operator's fault or SIM.
2. Install a network testing app, such as Network Signal Guru or CellMapper, to check the stability of the connection.
3. View the modem logs through the engineering menu (enter ##4636## and select Phone Information).

⚠️ Note: If you see errors in the engineering menu RRC Connection Failure or Modem Crash is a clear sign of hardware malfunction. Self-repair can make the problem worse - contact the service center.

6.Alternative solutions: from Wi-Fi Calling to operator change

If standard methods don’t work, consider these options:

• 📞 Wi-Fi Calling: Allows you to make calls over Wi-Fi without affecting mobile internet. → SIM-maps and mobile networks → Wi-Fi Calling. Supported by most modern Xiaomi and operators (MTS, MegaFon, Beeline).
• 🔄 The “Only” regime 4G»: Forced network installation 4G in settings (Settings) → SIM-map → Preferred type of network → Only LTE). Disadvantages: calls may not pass if the operator does not support VoLTE.
• 🏠 Home Wi-Fi: If the problem only manifests itself at home, connect to your home Wi-Fi network before calling. Many instant messengers (WhatsApp, Telegram) allow you to make Wi-Fi calls without losing mobile internet.
• 📡 Operator change: Some providers are better optimized to work with Xiaomi.Tele2 and Yota, for example, often offer more stable VoLTE than the "big three».

⚠️ Note: When using Wi-Fi Calling, make sure your router does not block UDP-Ports 500 and 4500 (required for the IP-If calls are interrupted, try to turn off the firewall on the router.

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Wi-Fi Calling is the best solution for users with unstable VoLTE, and it works even on older Xiaomi models, where there is no support for voice calls over 4G.

7.When to contact the service center

If you’ve tried all the methods, but the internet still shuts down when you make calls, it could indicate:

• 🔧 Damage to the modem chip (relevant after falls or moisture infestation).
• 🔋 Battery malfunction, due to which the phone cannot cope with the load on the modem.
• 📶 Programmatic failure at the level EFS-section (responsible for IMEI and network settings).

Signs that it is time to carry the phone for repair:

• The problem arose after mechanical damage (impact, fall).
• The phone doesn’t “see” the network even after resetting.
• The engineering menu (#4636##) displays modem errors.
• SIM-The card works on other phones, but not on your Xiaomi.

The average cost of diagnostics in Xiaomi service centers is from 500 to 1500 rubles. Repair of a modem chip will cost 3000-8000 rubles depending on the model. If the phone is warranty, do not try to disassemble it yourself - this will void warranty obligations.

FAQ: Frequent questions about the problem