Why the Internet turns off on Android MTS when making a call

The situation when the mobile data disappears during a voice call on a smartphone is one of the most common problems among subscribers of the MTS operator. Users notice that the 4G or LTE icon changes to 3G or E, and applications stop updating, making it impossible to use a navigator or instant messengers during a conversation. This is not a breakdown of your device or a malfunction of the operator's default network.

The main reason lies in the architectural features of cellular communications and methods of voice and data transmission. In old communication standards, voice and the Internet worked on different “channels”, and the phone physically could not serve them simultaneously without special technologies. However, modern smartphones and fourth-generation networks solve this problem if the parameters are configured correctly.

In this article we will analyze in detail the technical reasons for the connection loss, check the settings of your Androidsmartphone and learn how to activate the technology VoLTE for stable network operation during a call. You will understand whether the problem depends on the phone model, firmware version or type of installed SIM card.

Technical reasons for connection loss: CSFB and 2G/3G networks

To understand the essence of the problem, you need to turn to the history of the development of cellular networks. 2G (GSM) and 3G (UMTS) technologies were initially designed so that a voice call occupied the entire dedicated communication channel. When you made a call, the network forced the phone into voice mode, disabling packet data. This mechanism is called CSFB (Circuit Switched Fallback).

When using the 4G (LTE) network, the situation has changed, since this technology was originally created for data transmission. Voice in “pure” LTE is transmitted as a regular data stream via the Internet protocol. However, if this function is not activated, the phone, when making an incoming or outgoing call, “falls” down the network level - from fast 4G to slow 3G or even 2G to provide voice communication. It is at this moment that the Internet “falls off.”

The operator MTS, like other major market players, is gradually introducing voice transmission technologies over LTE. But this requires the coincidence of several conditions: support from the tower, support from the phone and correct tariff settings. If at least one link of this chain falls out, the rollback mechanism is triggered and you are left without the Internet.

⚠️ Attention: In some remote areas or areas of poor reception, operator towers may not support VoLTE technology. In this case, the phone will automatically switch to 3G when making a call, and disconnecting the Internet will be inevitable, regardless of the smartphone settings.

It is also worth considering that the old SIM cardsthat you have been using for years may not support the new authentication protocols necessary for simultaneous operation of voice and data on 4G networks. Replacing the plastic with a new one in a communication store often solves the problem instantly.

The role of VoLTE technology in solving the problem

The key solution to the problem of Internet shutdown is technology VoLTE (Voice over LTE). It allows you to transmit voice signals in the form of digital data packets directly over the 4G network, without switching your phone to outdated standards. With VoLTE active, you can talk and surf the Internet at high speed at the same time.

For this feature to work, it is necessary that the operator MTS supports it in your region. Today, this operator’s VoLTE coverage is quite wide in large cities. However, network support is only half the battle. Your smartphone must also have the appropriate module and software.

Many users do not know whether they have this function enabled by default. In modern versions Android the setting is often hidden or activated automatically when the SIM card is installed. But in some cases, especially on custom firmware or phones imported from other regions (for example, Chinese versions without global firmware), the option must be enabled manually.

Activating VoLTE not only solves the problem with the Internet, but also significantly improves sound quality. The voice becomes clearer and more natural, and the connection is established faster - in 1-2 seconds instead of the usual 5-7 seconds of waiting for beeps.

Checking the network settings on an Android smartphone

The first step in diagnosis should be checking the mobile data settings on your device. Often, users accidentally switch the network mode to “3G Only” or “2G Only,” which makes it impossible for the Internet to work during a call. You need to make sure that the mode that supports 4G is selected.

To do this, go to the settings menu of your device. The path may differ slightly depending on the phone model and shell version, but the general logic remains the same. You need to find the section responsible for connecting to the cellular network.

Follow these steps:

• 📱 Open Settings and go to section Connections or Network and Internet.
• 📶 Select item Mobile network or SIM cards and mobile networks.
• 🌐 Click on Network mode or Type network.
• ✅ Make sure that the option is selected LTE/3G/2G (auto-connect) or 4G Preferred.

If there is no mention of LTE or 4G in the list of available modes, this may mean that your smartphone does not technically support fourth generation communications, or there is no coverage in the region. In the first case, the solution to the problem is only possible by replacing the device.

It is also worth checking the access point (APN) settings. Sometimes resetting the access point settings to factory defaults helps restore correct Internet operation. To do this, in the mobile networks menu, find the item Access points (APN), open the menu (three dots in the corner) and select Reset settings.

How to enable VoLTE on different phone models

Interface for enabling the voice function Calls via LTE differ from manufacturer to manufacturer. On some devices this option is prominently displayed, on others it is hidden in the engineering menu or is completely absent from the standard interface.

In most cases, the switch is located in the same menu where you selected the network type. Look for the item with the name VoLTE, Calls via LTE or Improved 4G quality. If you do not find such a switch, try searching through your phone settings by entering the word “VoLTE”.

Below is a table with approximate ways to enable the function for popular brands:

Smartphone brand	Path to setting up VoLTE	Features
Samsung	Settings → Connections → Mobile networks → Calls via LTE	Can be called “Voice calls over LTE”
Xiaomi / Redmi	Settings → SIM cards and mobile networks → Use VoLTE	On some models hidden in the engineering menu
Huawei / Honor	Settings → Wireless networks → Mobile network → Calls VoLTE	Often enabled by default
Realme / OPPO	Settings → Mobile network → SIM card → Allow VoLTE	Requires operator support

On smartphones Xiaomi i Poco with global firmware, the function usually works immediately with the MTS SIM card. However, on Chinese versions (CN ROM), the switch may be hidden. In this case, you need to enter a special command through the engineering menu, but this must be done with caution.

⚠️ Attention: Interfering with the phone's engineering menu can lead to unstable communication or loss of warranty. If you are not sure of your actions, it is better to contact a service center or use standard settings.

Secret code to enable VoLTE on Xiaomi

On some Xiaomi models, you can try entering the code ##86583## in the dialing menu. If the message “VoLTE Carrier Check was disabled” appears, then the hidden restriction has been removed and the switch should appear in the settings. However, this method does not work on all firmware versions.

The influence of the SIM card and MTS tariff plan

Even with a modern smartphone and the correct settings, the problem may persist due to an outdated SIM card. The operator MTS periodically updates its security standards and communication protocols. Old plastic cards issued 5-7 years ago may not physically support the necessary algorithms for working in 4G networks with simultaneous voice transmission.

In addition, some archived tariff plans may have restrictions on the use of VoLTE technology. Although the operator is gradually transferring all subscribers to new conditions, it is worth checking the relevance of your tariff in the personal account of the My MTS application.

What to do if suspicion falls on the SIM card?

• 🔄 Try moving your SIM card to another modern smartphone with VoLTE support.
• 📞 If the problem persists, contact the MTS communication salon to replace the SIM card with a new one (USIM) for free.
• 💳 Make sure that there are enough funds on your balance and Internet services are active.

The procedure for replacing a SIM card takes only a few minutes in the salon if you have a passport. The new card will have improved signal reception characteristics and full compatibility with modern data transmission standards.

It is also worth noting that when using two SIM cards, the Internet may turn off during a call if the call is made through the second SIM card, and Internet is set to first. Make sure that the correct data slot is selected in the mobile network settings or the simultaneous operation function is enabled (if the phone supports Dual 4G).

Alternative solutions and the use of instant messengers

If technical means cannot solve the problem (for example, the phone does not support VoLTE or there is no 4G coverage in your area), there are workarounds. The easiest way to stay connected to the Internet during a conversation is to use instant messengers.

Applications like WhatsApp, Telegram or Viber they use exclusively the Internet channel for calls. If you make a call through them, the mobile network does not switch to voice mode and the 4G icon remains active. This allows you to use a browser or navigator in parallel.

However, this method requires a good quality Internet connection. If you are in an area with poor reception, the quality of voice communication in instant messengers may be lower than with a regular phone call. In addition, the interlocutor must also have the application installed and access to the Internet.

Another option is to use technology Wi-Fi Calling. If your smartphone and carrier support this feature, you can make regular phone calls over Wi-Fi. In this case, the mobile network is not used for voice at all, and the mobile data remains available, even if you are in an area of ​​poor cellular reception.

⚠️ Attention: The charging conditions for calls via Wi-Fi Calling may differ from regular calls. Check with your MTS operator whether this service is included in your tariff and how it is charged to avoid unexpected expenses.

Frequently asked questions about turning off the Internet when making a call

Why does the Internet still turn off on my new phone?

Even on new devices, the VoLTE function may be disabled by default by the manufacturer or operator. Check your mobile network settings and make sure the VoLTE switch is enabled. Also try restarting your phone after inserting the SIM card.

Does the Android version affect the Internet during a call?

Yes, older versions of Android (below 7.0) may not have full VoLTE support or require complex settings. On Android 10 and higher, this function usually works stably if there is hardware support.

Can I turn on the Internet manually during a call?

No, if the phone switches to 2G/3G mode for a voice call (CSFB), you will not be able to turn on the Internet manually, since the physical channel is occupied by voice. Only activating VoLTE will help.

Will the Internet work if I answer a call through a Bluetooth headset?

Using a headset does not affect the type of network. If the phone does not support VoLTE, the Internet will turn off regardless of whether you are talking on the phone, through headphones or on the speakerphone.

How much does the VoLTE service cost from the MTS operator?

The VoLTE service is provided to MTS subscribers free of charge. The only condition is the presence of a supporting device, a modern SIM card and a tariff plan that allows the use of this technology.