Xiaomi Mi 9T Pro (aka Redmi K20 Pro in some regions) is the flagship smartphone of 2019, which is still relevant today thanks to the powerful hardware and support of modern communication technologies. One of them is VoLTE (Voice over LTE), which allows you to call over 4G network without falling Internet speed. However, many users are faced with the fact that the feature is either missing in the settings or does not work after activation.
In this article, we will discuss all ways to enable VoLTE on Mi. 9T Pro, including hidden settings MIUI, Checking for operator compatibility and solutions for cases where the option is gray or disappears after the update, you will also learn how to distinguish real VoLTE from pseudo-do.-4G» Calls and why some of them SIM-The card does not support the technology despite the statements of the operator.
The instructions are valid for all versions of MIUI 12, 13 and 14 firmware based on Android 10–13, as well as for global, European and Chinese versions of the smartphone (codenames: raphael, raphaelin). If your operator officially supports VoLTE, but the function does not work, here you will find a solution.
What is VoLTE and why should it be included on the Mi 9T Pro?
VoLTE (Voice over LTE) is a 4G voice technology that replaces the outdated 2G/3G standards. Unlike conventional calls, where the smartphone switches to slow networks, VoLTE keeps high-speed Internet during a conversation and improves the quality of communication.
On Xiaomi Mi 9T Pro with Snapdragon 855 processor and X24 modem, the technology works stably, but its support depends on three factors:
- 📱 Hardware compatibility – the smartphone should support VoLTE in your region (on the Mi) 9T Pro this is implemented at the level of iron).
- 📶 Operator support – not all mobile networks provide a service (for example, in Russia, VoLTE actively use MTS, Beeline, Tele2, and MegaFon selectively).
- 🔧 Firmware settings - in MIUI The option can be hidden or disabled by default.
Important: on Mi 9T Pro with Chinese firmware (without global firmware) ROM) VoLTE may not work even with operator support - it requires unlocking the bootloader and installing custom firmware with the correct one. IMS-certificate.
The advantages of VoLTE on the Mi 9T Pro:
- ⚡ Instant connection – the call is connected to 1–2 seconds against 5–10 second-in-second 2G/3G).
- 🎙️ Pure sound - wide band of frequencies (HD Voice) eliminates noise and echo.
- 📶 Without losing the internet, you can talk and use it at the same time. 4G (For example, viewing maps or chats).
- 🔋 Saving charge – no need to switch between networks, which reduces the load on the modem.
Verification of VoLTE support by your operator
Before setting up your smartphone, make sure your mobile operator supports VoLTE in your area. Here are the latest data on popular providers (2026):
| Operator. | Support for VoLTE | Regions of coverage | Required SIM-map |
|---|---|---|---|
| MTS | ✅ Yes. | All of Russia, except remote areas | USIM (4G) |
| Beeline | ✅ Yes. | Large cities (Moscow, St. Petersburg, millionaires) | USIM or eSIM |
| Tele2. | ✅ Yes. | 70+ regions (full list on the site) | USIM (required) |
| MegaFon | ⚠️ Partially. | Moscow, St. Petersburg, Krasnodar, Sochi | USIM with IMS support |
| Yota | ❌ No. | — | — |
To find out if VoLTE is available for your number:
- Send. USSD-request: MTS: *111*59# Beeline: *110*180# Television2: *155*1#
Check your personal account on the operator’s website in the “Services” or “Tariff” section.
"Voice over 4G"
«VoLTE»
⚠️ Note: If you use a virtual operator (Tinkoff Mobile, SberMobail, Loco), VoLTE is probably not available – these companies rent networks from major providers without support. IMS-protocol.
Step-by-step: how to turn on VoLTE on Xiaomi Mi 9T Pro
If the operator supports the technology, move to the setting of the smartphone. on the Mi 9T Pro there are two ways to activate VoLTE: through the standard menu and using the engineering mode (if the option is hidden).
Method 1: Standard MIUI settings
This method works on most firmware versions (MIUI 12–14):
- Open the Settings. → SIM-maps and mobile networks.
- Choose yours. SIM-card (if two of them).
- Tap on the network type (or preferred network type).
- Enable the VoLTE option (the slider must turn blue).
- Go back and activate improved calls or HD-calls (if any).
Method 2: Engineering menu (for hidden settings)
If VoLTE is not in the standard settings, try enabling it through the engineering menu:
- Open the phone app and enter the combination: ##4636##
- In the menu that opens, select Phone Information (or Phone Information).
- Scroll down to the Set preferred network type section.
- Select LTE only or LTE/WCDMA/GSM auto.
- Activate the option of VoLTE provisioned (if any).
- Reboot your smartphone.
Note: On some versions MIUI The engineering menu may be missing or require root rights. USSD-codes (see next section).
☑️ Preparation for the inclusion of VoLTE
USSD-codes for forced inclusion of VoLTE
If standard methods don’t work, try activating VoLTE using service commands, which work on most Mi 9T Pro firmware, but may vary by region:
- 📞 Activation of VoLTE: ##86583## (enter in dial number and click "Call»).
- 🔄 Resetting settings IMS: ##4636## → IMS Service Status → Reset IMS.
- 📡 Checking the registration in the VoLTE network: ##4636## → IMS Registration Status (must be Registered).
- 🔧 Forced network selection LTE: ##4636## → Set preferred network type → LTE only.
After entering each code, wait for the notification of successful activation or restart your smartphone.
- Your firmware blocks engineering commands (the solution is to upgrade MIUI or install custom firmware).
- The operator does not support VoLTE for your SIM-Cards (call in support).
⚠️ Attention: Do not use USSD-codes from unknown sources – some commands (e.g. ##7780##) can reset your smartphone settings to factory settings. 9T Pro.
Solving problems: VoLTE is not turned on or is lost
If after all the manipulations VoLTE and did not work, check the following points:
| Problem. | Possible cause | Decision |
|---|---|---|
| Option VoLTE gray color | SIM-card does not support IMS | Replace SIM with USIM in the operator’s cabin |
| VoLTE is turned on but does not work | Inactive service from the operator | Activate via USSD or personal account |
| Calls pass, but no calls. HD-sound | Not included are "Improved Calls" | Include in Settings → Sound → Call quality |
| VoLTE disappears after update | Resetting IMS settings | Enter ##4636## → Reset IMS |
Additional steps to troubleshoot:
- Check that you have the latest firmware version installed (Settings → About Phone → System Update).
- Reset network settings: Settings → SIM-map → Resetting mobile network settings.
- Remove and add again SIM-map in settings (Settings) → SIM-map → Management SIM-map).
- If you use two SIM-Please try leaving only one card (VoLTE may not work in Dual mode). SIM firmware).
What to do if the VoLTE is not working properly?
How to distinguish real VoLTE from pseudo-4G calls
Many users confuse VoLTE with regular 3G/2G calls, which simply appear as "4G" on the screen.
- 📊 Check the network indicator: during the call next to the signal level should appear the inscription HD, VoLTE or icon 🎙️.
- 📶 Use the engineering menu: Enter ##4636##. IMS Registration Status: Make sure that the Registered Status (not Not Registered Status).
Check the speed of the Internet
Speedtest
Test call
If you have a VoLTE indicator, but calls are made through 3G, then:
- The operator uses CSFB (Circuit Switched Fallback) - temporary switching to 3G for calls.
- In your region, VoLTE is running in test mode (check with the operator).
- SIM-card does not support IMS-Profile (replace it in the salon).