The experience of suddenly losing mobile service inside a building is familiar to many subscribers. The thick walls of modern offices, basements, or remote country houses often become "dead zones" where a standard cell tower signal simply doesn't penetrate. In such cases, technology comes to the rescue. Voice over Wi-Fi, which allows you to make and receive calls over a wireless network.
MTS is actively implementing and supporting this feature, calling it "MTS Wi-Fi Calling." It's not just an alternative to calls through messaging apps like Viber or WhatsApp, but a fully-fledged voice call replacement integrated into the standard phone interface. You don't need to open additional apps or ask your caller to install the same software—your number remains your regular one, and you're charged according to your basic plan.
Activating this option requires meeting several conditions, both for the subscriber number and the equipment used. In this article, we'll detail the technical requirements, walk through the step-by-step setup process on different operating systems, and answer frequently asked questions about the service while roaming and when switching between networks.
What is VoWiFi technology and how does it work at MTS?
Technology Voice over Wi-Fi (VoWiFi) is the transmission of voice traffic and SMS messages over IP, using the internet instead of the cellular network's radio channel. For the operator, this is a way to relieve the load on base stations in crowded areas, and for the user, it guarantees connection in areas where the phone previously showed "No Service." MTS often combines this service with the concept HD Voice, providing high sound quality.
The principle of operation is to create a secure tunnel between your device and the operator's gateways. When you dial a number, the signal travels through the router to the internet, then to MTS servers, and is then routed to the public telephone network. It's important to understand that the service requires a stable internet connection with low latency (ping).
⚠️ Please note: Call quality directly depends on the speed and stability of your Wi-Fi connection. If your internet connection is heavily loaded with downloading large files or watching 4K videos, voice communication may be choppy or tinny.
Unlike app-based calls, VoWiFi works at the operating system level. This means you can switch between calls and contacts, use speakerphone, and other system features without restrictions. Furthermore, this technology is crucial for those roaming: incoming calls to a number in your region via Wi-Fi are often charged at the same rate as domestic calls, even when you're abroad, allowing for significant savings.
Requirements for the subscriber's device and SIM card
Before proceeding with settings, you need to ensure that your equipment supports IMS (IP Multimedia Subsystem) networks, which underpin VoWiFi. Not all smartphones, even modern ones, have software support for this feature in firmware adapted for Russian operators.
First, check your device model. The technology is supported by most flagship and mid-range models released in the last 3-4 years. Pay special attention to the software version—sometimes support only appears after updating to the latest available version. Android or iOS.
The SIM card must also meet certain standards. If you're using an old plastic card that was cut with scissors, or a SIM card that's more than 5-7 years old, you may have problems registering with the IMS network. In this case, it's recommended to replace the card with a new one at a mobile store or through the operator's app, keeping your number.
- 📱 The smartphone must support the 4G (LTE) standard and have an unlocked SIM card slot.
- 📶 Your device must have 4G/LTE enabled and data transfer permitted.
- 🆔 The SIM card must be registered to the owner and not blocked by the operator.
- 🌐 Data roaming must be activated in your phone settings (even for calls within your home region).
The situation with push-button telephones and devices based on them deserves special mention. KaiOSAlthough some models support VoLTE, VoWiFi functionality is extremely rare and depends on the specific device model. To fully utilize the service, it's best to use a smartphone.
Step-by-step activation of the service on the operator's side
The "Wi-Fi Calling" service itself must be activated in the subscriber's profile. MTS has simplified this process as much as possible and often occurs automatically during the first setup attempt on a compatible device. However, if automatic activation fails, it can be forced.
The fastest way is to use a USSD command or your personal account. You can send a request through your phone's menu, which will instantly activate the service. You can also manage it through the "My MTS" mobile app, where you'll find a toggle for internet calls in the services section.
*111*879#After entering this command, a notification will appear on the screen indicating successful connection. If the service is already active, the system will notify you of this.
In some cases, especially when using corporate plans or older archived plans, automatic connection may be blocked. In this case, you'll need to contact support via chat or voice call to manually activate the VoWiFi profile on the server.
Setting up Wi-Fi calling on Android
The setup interface on smartphones with the operating system Android The procedure may vary depending on the manufacturer and operating system version (MIUI, OneUI, ColorOS, etc.). However, the logic remains the same for all devices. First, make sure your mobile data connection is enabled, as the system checks for network availability before activating the tunnel.
Go to your phone's main settings and find the section responsible for SIM cards and mobile networks. The path may look like this: Settings → Connections → Mobile networks or Settings → SIM cards and mobile networksThis is where the switch you need is hidden.
Find "Wi-Fi Calling" and enable it. The system may prompt you to select a network priority. We recommend setting it to "Prefer Wi-Fi" or "Always use Wi-Fi" if you're in an area with poor cellular service but excellent Wi-Fi coverage.
☑️ Android Setup Checklist
If you can't find this option in the standard menu, try searching through the settings. Enter "Wi-Fi" or "VoWiFi" in the search bar, and the system will automatically direct you to the correct section. On some devices (e.g., Xiaomi or Samsung), you may need to additionally activate the feature in the Phone app menu by clicking the three dots in the corner of the screen.
⚠️ Note: On some Chinese smartphones (global firmware versions), the menu may be in English. Look for the "Wi-Fi Calling" or "VoWiFi" option. If there's no option at all, your model may not be certified for this mode with Russian carriers.
Instructions for iPhone (iOS) owners
For smartphone owners Apple We're lucky in terms of interface unification. On all iPhone devices, starting with the 6s and supporting current versions of iOS, setup is handled in a single menu. The main requirement is having the latest available version of the operating system installed.
To activate, open Settings → CellularIf you have two SIM cards (a physical one and an eSIM), select the one from MTS. In the menu that opens, find the "Wi-Fi Calling" toggle and turn it on. The system may warn you that Wi-Fi calls may transmit location information—this is necessary for emergency services. Accept the terms.
Once enabled, the status bar (at the top of the screen) will display "MTS Wi-Fi" or a handset icon with the word "Wi-Fi" next to the operator's name. This indicates that the phone is ready to make calls over the wireless network. If the icon doesn't appear, try toggling Flight Mode on and off.
What should I do if there is no "Wi-Fi Calling" option on my iPhone?
Make sure you're signed in to iCloud. Sometimes you need to update your carrier settings: Settings → General → About this device → (If prompted to update carrier settings, agree). Also, check that the service is enabled in your MTS account.
A unique feature of iOS is that when switching between Wi-Fi and cellular data during a call, the call is not interrupted, but seamlessly switches to the other connection type if coverage allows. This ensures uninterrupted communication when leaving the house.
Comparing VoWiFi and messaging calls
Many users confuse VoWiFi technology with traditional calls via WhatsApp, Telegram, or FaceTime. Although both methods technically use the internet, the difference for the subscriber is significant. Below is a table demonstrating the key differences.
| Characteristic | VoWiFi (MTS) | Messengers (WhatsApp, TG) |
|---|---|---|
| Call ID | Your real phone number | Account/Nickname in the application |
| Availability of the interlocutor | Call any number (landline or mobile) | Only if the other person has the same app installed |
| Tariffs | According to the rates of your minutes package | Traffic consumption (or free) |
| Working in roaming | Incoming calls are often free, like at home | Always free (only Wi-Fi required) |
The main advantage MTC Wi-Fi Calling The advantage is transparency. You don't have to worry about whether your grandmother in the village has internet or Viber. You simply dial the number, and the call connects. Plus, your call history is saved in your phone's standard log, rather than getting lost in your chats.
On the other hand, messaging apps are superior in situations where the SIM card is blocked or the phone has no network coverage (airplane mode), but Wi-Fi is available. However, for everyday use, especially in areas with poor indoor coverage, VoWiFi is a more reliable and professional solution.
Common problems and solutions
Despite the technology's robustness, users may encounter difficulties. The most common issue is that the VoWiFi icon doesn't appear, even though all settings are correct. In 90% of cases, this is resolved by restarting the smartphone or re-entering the service's USSD activation code.
Another common scenario: a call drops when switching from Wi-Fi to a mobile network. This happens when the cell tower signal is too weak to transmit voice (2G/3G), and Wi-Fi suddenly disappears. In such cases, the phone doesn't have time to transmit the session, and the call is dropped. The solution is to force "4G/LTE Only" mode in the network settings so the phone doesn't try to connect to the unstable 3G network.
It's also worth considering the limitations of public networks. Cafes, airports, and hotels often use captive portals (login pages). Until you enter your password or click "Login" in your browser, VoWiFi won't work, as the tunnel to the operator's server is blocked.
⚠️ Please note: When calling emergency numbers (112, 102, 103) via Wi-Fi, the location may be inaccurate, as it is based on the router's IP address, not the tower's geolocation. Always confirm the address with the dispatcher.
If you're traveling abroad, be sure to check roaming conditions. While technology can save you money, some plans may have restrictions on VoWiFi use in certain countries. Check your carrier's app for current terms before traveling.
Questions and Answers (FAQ)
Do you charge for Wi-Fi calls when roaming?
As a rule, when roaming, incoming calls via Wi-Fi to an MTS number are charged the same as if you were in your home region (often free or according to your plan's terms). Outgoing calls may also be charged at home rates, but these may vary depending on the country of residence. It's recommended to check the information in the app before calling.
Does making Wi-Fi calls use up mobile data?
No, traffic is transmitted via your Wi-Fi connection and does not consume your mobile data plan. However, a minimal amount of data (a few kilobytes) may be used for initial network registration and service availability verification.
Can I use VoWiFi if I have an ad blocker on my phone?
Ad blockers and DNS filters (such as AdGuard) can block connections to the operator's servers required to establish a voice tunnel. If calls aren't going through, try temporarily disabling ad blockers or adding the operator's domains to exceptions.
What should I do if the VoWiFi setting is missing after updating iOS/Android?
After major operating system updates, network settings may reset. Go to the SIM card menu and re-enable the "Wi-Fi Calling" toggle. If the option is missing, check for carrier settings updates in "General → About" (on iOS) or reset your network settings.