Wi-Fi Calling on Redmi 9: Full Setup + Troubleshooting

Xiaomi Redmi 9 - one of the most popular budget smartphones that supports technology VoWiFi (Voice over Wi-Fi). This feature allows you to make calls over the internet even without a mobile network, saving battery life and improving call quality in areas with poor coverage. However, many users encounter difficulties setting it up: in some cases, a menu option is missing, in others, the carrier doesn't support the technology, and in others, calls simply don't connect.

In this article we will look at All ways to activate VoWiFi on the Redmi 9 (including models Redmi 9A/9C/9T), we will consider the requirements of Russian operators (MTS, Beeline, MegaFon, Tele2), and also provide a checklist for troubleshooting. We will pay special attention hidden MIUI settings, which the manufacturer does not advertise, but which can save the situation if the standard method does not work.

What is VoWiFi and why is it important for the Redmi 9?

Technology VoWiFi (or Wi-Fi Calling) allows you to make voice calls and send SMS over the Internet using your home or office Wi-Fi network. For Redmi 9 This is especially relevant for three reasons:

• 📶 Weak mobile network signal: Budget chipset MediaTek Helio G35/G80 The Redmi 9 doesn't always have reliable network coverage in basements or on the outskirts of cities. VoWiFi solves this problem.
• 🔋 Battery savingWhen making calls via Wi-Fi, your smartphone does not waste energy searching for and maintaining a cellular network, which increases battery life by 15–20%.
• 💰 Free calls while roaming: Many operators (for example, MTS) do not charge for VoWiFi calls abroad if the corresponding tariff is connected.

It is important to understand that VoWiFi is not the same as instant messengers (WhatsApp, Viber). Calls are made through your main phone number, not through your app account. This means:

• ✅ Call history is saved in the standard Phone app.
• ✅ Caller ID and spam blocking are working.
• ✅ No need to install additional programs.

⚠️ AttentionNot all carrier plans support VoWiFi. For example, MegaFon only offers this feature on its "All Inclusive" and "Unlimited" plans, while Tele2 only offers it for subscribers with the "Wi-Fi Calling" option. Check the terms in your personal account or with your carrier.

Requirements for setting up VoWiFi on Redmi 9

Before enabling Wi-Fi calling, please check that your smartphone and plan meet the following requirements:

If any of the above points are not met, VoWiFi will either not turn on or will work intermittently. For example, on Redmi 9A With MIUI 11, the function may not be available in the menu, but Redmi 9 Pro with custom firmware - require additional settings.

Critical remark: On some firmware versions from Xiaomi The "Wi-Fi Calling" option is hidden, even if the phone supports the technology. This is due to operator policies in certain regions. In this case, manual activation via the engineering menu (more on this in the next section).

Method 1: Standard VoWiFi setup in MIUI

If your Redmi 9 meets all the requirements, try enabling the function through the main settings:

1. Open the app Settings (gear icon).
2. Go to the section Connections and Sharing → SIM Cards and Mobile Networks.
3. Select your SIM card (if you have two).
4. Tap on the item Wi-Fi calling (or Wi-Fi Calling).
5. Activate the switch and select the mode:
   • Wi-Fi only — calls only via the Internet.
   • Wi-Fi is preferred — first tries Wi-Fi, then the cellular network.
   • Cellular network is preferred — Wi-Fi is used only when there is no coverage.

Once enabled, an icon will appear in the status bar (upper right corner of the screen) Wi-Fi with a handset or an inscription VoWiFiIf the icon is missing but the feature is enabled, don't worry: on some firmware versions, the indicator won't be displayed.

Turn off your mobile data (Airplane mode with Wi-Fi enabled) | Call another phone | Check that the Wi-Fi icon is displayed in your call history | Make sure the other person's voice is clear and free of interference -->

What should I do if the "Wi-Fi Calling" option is not available in the menu? This is a common problem on Redmi 9 with firmware for specific regions. Solutions:

• 🔄 Update MIUI to the latest version (even if the system says there are no updates, check manually in Settings → System update → Three dots → Select update package).
• 📱 Install global firmware (if you have a regional version).
• 🛠️ Use the engineering menu (instructions in the next section).

Method 2: Manual activation via the engineering menu (for advanced users)

If the standard method does not work, you can activate VoWiFi via engineering menu (Engineer Mode) This method is suitable for Redmi 9/9A/9C/9T at the base MediaTek, but requires caution - incorrect settings can disrupt the network.

Instructions:

1. Open the app Telephone and enter the combination:

   ##4636##

   If the code didn't work, try:

   ##36446337##

2. In the menu that opens, select Phone information (or Phone Information).
3. Scroll down to the block VoWiFi or IMS Service Status.
4. Tap on Enable VoWiFi (or Turn on VoWiFi).
5. Return to the main menu and select Network settings (Network Setting).
6. Install Preferred network type V LTE/UMTS auto (PRL).
7. Restart your phone.

After rebooting, check if the VoWiFi icon appears in the status bar. If not, try making a test call with your mobile network disabled (enable Airplane mode and connect to Wi-Fi only).

⚠️ Attention: Changes in the engineering menu may cause the modem to malfunction. If the mobile network is lost after these changes, reset the network settings. Settings → SIM cards & mobile networks → Reset network settings.

adb shell am start -n com.mediatek.engineermode/.EngineerMode

Operator requirements: how to connect VoWiFi to MTS, Beeline, MegaFon, and Tele2

Even if the phone supports VoWiFi, the operator can block the function At the SIM card or plan level. Below are the current terms and conditions for major Russian providers (data subject to change, please check in your personal account!).

If you have corporate SIM card or a plan older than 2019, VoWiFi may not be available. In this case:

• 📞 Call your operator and request activation (sometimes this is done manually).
• 🔄 Change your tariff to a newer one (for example, with MTS, switch to "MTS Smart").
• 🆔 Check if the service is blocked in your region (this applies to Crimea and the Donetsk People's Republic/Luhansk People's Republic).

Troubleshooting: Why Wi-Fi Calling Isn't Working on the Redmi 9

If VoWiFi is enabled but calls are not going through, use these diagnostic instructions:

Problem 1: The VoWiFi icon is present, but calls are made via the cellular network.

Possible causes and solutions:

• 🔌 Wi-Fi is connected, but there is no internet access.Check if websites open in your browser. If not, reboot your router.
• 📵 VoLTE is disabled: VoWiFi requires activation VoLTETurn it on. Settings → SIM cards → 4G calling (VoLTE).
• 🔄 IMS service outage: Go to Settings → Applications → Manage applications → Three dots → Show system, find IMS Service and clear the cache.

Problem 2: VoWiFi turns on but immediately turns off

This is a typical mistake on Redmi 9 with custom firmware. Solutions:

• 🛠️ Reset network settings: Settings → SIM cards → Reset network settings.
• 📥 Install the latest version MIUI through System update.
• 🔧 Turn it off dual Wi-Fi (if enabled): Settings → Wi-Fi → Advanced → Dual Wi-Fi.

Problem 3: When calling, the other person can't hear you or hears a robot

This is related to voice communication codecsWe are fixing:

1. In the engineering menu (##4636##) go to Audio.
2. Select VoIP Call.
3. Install VoIP Codec Priority V EVS or AMR-WB.
4. Save the settings and restart your phone.

⚠️ Attention: If after changes in the engineering menu the sound in calls has disappeared, reset the sound settings to default in Settings → Sound → Reset sound settings.

VoWiFi Alternatives: What to Do If It's Not Working

If on yours Redmi 9 If you still can't set up VoWiFi, consider alternative methods of making calls over the internet:

• 📱 Google Fi (for international travel)This Google service allows Wi-Fi calling in over 200 countries. Requires a US SIM card or eSIM.
• 💬 Messengers with call support:
  • WhatsApp — free calls worldwide.
  • Telegram - low traffic consumption.
  • Viber - the best sound quality.
• 📞 Applications from operators:
  • MTS Connect - calls via Wi-Fi even without VoWiFi.
  • Beeline Prostor — an alternative for corporate clients.
• 🔄 SIP telephony: Set up an account in Zoiper or Linphone with any SIP provider (for example, Sipnet).

The advantage of instant messaging apps is that they work on any phone, but they also have their downsides:

• ❌ The other person you're talking to must also use this app.
• ❌ The phone number is not displayed (call from your account, not from your SIM card).
• ❌ Quality depends on the messenger's servers.

FAQ: Frequently asked questions about VoWiFi on the Redmi 9