Mobile communication has long since ceased to be just voice, becoming a complex digital process, where the sound quality depends directly on the technologies used. For owners of Xiaomi smartphones and MTS subscribers, the use of VoLTE (Voice over LTE), which allows voice calls through fourth-generation networks, is critical, not just a marketing ploy, but a real necessity, providing crystal clear sound and instant connection without falling into 2G or 3G.
However, despite the ubiquity of 4G networks, many users are faced with a situation where the HD or VoLTE icon does not appear automatically in the status bar. Owners of Redmi and Poco devices often have to resort to manual settings, since the standard MIUI or HyperOS menus can hide the necessary switches, our goal is to understand the activation process in detail so that you can enjoy the full benefits of modern communication.
Before you start complex manipulations with the engineering menu, you need to make sure that your SIM-The MTS operator provides this opportunity for free for most modern tariffs, but technical support on the subscriber side requires a number of conditions. Below we will consider each stage of preparation and setting up in as much detail as possible.
Equipment and tariff requirements
The first step is to check your device’s technical compatibility with the carrier’s networks. Not every smartphone, even if it supports 4G, can work correctly with the voice protocols of a particular provider. To successfully activate VoLTE on Xiaomi, you need the device to be certified on MTS networks or have an unlocked engineering interface for manual settings input.
It is important to understand that SIM-If you use old plastic that's been cut from a larger card or just been in use for more than five years, replacing it can be a must. USIM Improved protection and support for advanced voice traffic encryption algorithms.
In some remote areas where the 4G network is unstable or on the verge of coverage, the phone can force the switch to 3G to ensure communication stability, ignoring the VoLTE settings. In such cases, the HD icon can appear and disappear, which is normal system behavior.
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Replace. SIM-card in the salon of MTS free of charge if it is older than 3 years - this often solves problems with registration in networks 4G.
Basic settings through the standard menu
Let’s start with the simplest and safest method, which is suitable for most current Xiaomi, Redmi and Poco models. Manufacturers often hide the VoLTE switch in the depth of settings, so as not to overload the interface with unnecessary elements for untrained users. You will need to open the Settings app and go to the section SIM-maps and mobile networks.
Select the MTS SIM card if there are two of them in the device. In the menu that opens, find Use VoLTE or Enable VoLTE. If the switch is active and available to press, just activate it. After that, the corresponding icon should appear in the status bar, and calls will begin to pass through LTE.
In some versions of MIUI or HyperOS, this item can be hidden until you first log in. Try to turn on the flight mode for 10 seconds, then turn it off so that the phone re-registers on the network. Often after this procedure, the hidden switch becomes active.
- 📱 Open the Settings. → SIM-maps and mobile networks.
- 📡 Select the MTS SIM card from the list of available.
- ✅ Activate the switchboard Use VoLTE.
- 🔄 Restart the device to apply changes.
If the switch is missing or locked (gray), it means that the system has not detected an automatic configuration from the operator, in which case you should not despair, since there is a method of forced activation through the engineering menu, which we will discuss later.
☑️ Checking basic settings
Activation through the Engineering Menu (CIT)
When standard methods fail, Xiaomi’s engineering menu, known as the CIT (Customer Integration Test), is designed to diagnose hardware and software components, but also allows you to manage hidden modem functions.
Dial the combination ##6484##. If the menu is open, look for the SIM Card Test or Telephony option in the list. However, on new versions of Android, access to these functions through code may be limited. In this case, the more effective way is to use the MIUI Hidden Settings application or enter a command via ADB, but we will go the way that is available without a computer.
There is an alternative code to call the test menu: ##4636##. Once in the Testing menu, select Phone Information. Here, at the bottom of the screen, you can find the Turn on VoLTE Provisioned button or the Set Preferred Network Type drop-down. If you see the turn-on button, click it. If it's not there, go to the network type.
⚠️ Warning: Changing the settings in the engineering menu can lead to a temporary loss of communication. If you are not sure about your actions, write down the initial values before making changes to return everything as it was.
In the network type list, select the option that contains LTE/TD-SCDMA/CDMA/EVDO/GSM/WCDMA or simply LTE Preferred. The presence of an IMS prefix in the network mode name often indicates support for the multimedia subsystem required for VoLTE. Once the mode is selected, the network will reboot automatically.
What if the code doesn't work?
Using ADB to Unlock VoLTE
For advanced users who have not worked previous methods, remains the most reliable, but also more difficult way – the use of debugging on the Internet. USB and command line ADB (Android Debug Bridge. This method allows you to interact directly with the Android system settings database without the interface limitations. ADB and drivers for Xiaomi.
The first thing you need to do is activate the developer mode on your smartphone. To do this, quickly click seven times on the build number in the About Phone section. Then in the Advanced Settings menu → For developers, turn on Debugging over USB. Connect the phone to your PC with a cable and confirm the request for debugging permission on your smartphone screen.
Open the command line on your computer in the ADB folder and enter the following command to check the connection: adb devices. If the device is determined, you can proceed to enter commands to activate VoLTE. Commands may differ depending on the version of Android and the processor model (Snapdragon, MediaTek), but the basic set for Xiaomi looks like this:
adb shell settings put global carrier_volte_available 1
adb shell settings put global carrier_vt_available 1
adb shell settings put global carrier_wfc_ims_available 1After completing the commands, you need to restart the device. In some cases, you need to additionally activate the provisioning flag through the command: adb shell svc voice set-capabilities ims. If after the reboot the icon appears, but the calls do not pass, try resetting the network settings in the phone menu.
| ADB Team Team | Function | Necessity |
|---|---|---|
| carrier_volte_available | Allows the use of VoLTE | I'll be sure. |
| carrier_vt_available | Allows video calls via LTE | Optionally. |
| ims_required | Requires IMS for calls | Critically. |
| wfc_ims_available | Activate Wi-Fi calls | Additionally. |
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Using ADB is the most powerful tool to circumvent the manufacturer’s software limitations, but requires caution and PC availability.
Dual SIM Problems and Their Solutions
Xiaomi smartphone owners often use two SIM cards, which makes its own adjustments to the VoLTE. DSDS (Dual SIM Dual Standby) technology has limitations: at the same time in 4G mode, only one SIM card can work, or both, but with bandwidth restrictions. If one card is activated VoLTE, the second can force switch to 2G/3G during a conversation.
To minimize problems, it is recommended to assign the MTS card to the main data transfer. SIM-maps and mobile networks, install MTS in the mobile Internet. Also check that the settings of the second SIM card was not prohibited from using the mobile device. 4G, If you want to keep the internet fast on both lines (although it depends heavily on the capabilities of the particular modem).
Sometimes there is a conflict when the phone tries to register both SIM cards in VoLTE at the same time, but the operator network does not allow this or the modem does not cope, in such cases, it helps to temporarily disable the second SIM card to check the operation of the first, if one card VoLTE works perfectly, and when you turn on the second one disappears, the problem lies in the hardware limitations of the chipset of your smartphone.
- 📶 Install the MTS SIM card in slot 1 (main).
- 🌐 Assign MTS to the default card for mobile Internet.
- 📞 Check VoLTE with another operator’s active second SIM card.
- 🔄 If you have problems, try to change the SIM card slots in places.
⚠️ Note: On some Redmi and Poco models with MediaTek processors, simultaneous VoLTE running on two SIM cards may not be physically possible, regardless of the settings.
Diagnostics and troubleshooting
Even after you set up correctly, there can be situations where VoLTE stops working, often due to firmware updates that reset user configurations, or operator-side changes, and first check if you have power saving mode on, which can aggressively limit the background of the network.
Also worth noting is the availability of updates for the Settings app and Google Play system services. Sometimes bugs are hidden in the software responsible for interacting with network protocols. Resetting network settings to factory settings (Settings → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth) often helps to accumulate configuration errors.
If nothing works, your plan may be outdated and not support new services. Call MTS Support or use My MTS app to make sure that the service is connected on the operator's side. USSD-request to activate the service, even if it is free.