An instant drop in Internet speed to 3G or E immediately after dialing a number on an Android smartphone blocks loading pages, disables notifications in instant messengers and can interrupt the operation of the navigator, which is not caused by a device defect, but rather the peculiarities of switching network modes during a voice call.
The reason lies in the fundamental differences in how mobile networks transmit voice and data. In old communication standards, voice and Internet used different channels, and the phone physically could not be in two modes at the same time. Modern technologies make it possible to combine these streams, but this requires compliance with a number of conditions on the part of the operator, the tariff and the smartphone itself.
If you are faced with the fact that the Internet on your Android does not work when talking on the phone, do not rush to take the device for repair. In most cases, the problem can be resolved by changing a couple of settings or checking that your service provider supports the service. Let's look at the technical details and ways to fix this problem.
Technological reasons for the disconnection
Historically, mobile communications developed in stages. Second generation (2G) and third (3G) networks used different technologies for voice and data transmission. Voice was transmitted over circuit switching channels (Circuit Switched), and the Internet was transmitted over packet switching channels (Packet Switched). When you started a call on the network 3G, the phone switched to the voice channel, interrupting the data session.
With the advent of the standard LTE (4G), the network architecture changed. Here, it was initially planned to transfer only data, and the voice was supposed to flow as a regular flow of information via the Internet protocol. However, it took time for operators to upgrade the equipment. Before the introduction of technology VoLTE (Voice over LTE), when making a call, phones were forced to “roll back” down to the network 3G or 2G, where there is support for voice calls.
This switching process is called CSFB (Circuit Switched Fallback). This is the main reason why the Internet disappears when making a call. The phone temporarily leaves the high-speed network 4Gto establish a voice connection on the old network, where data transmission is either absent or extremely slow. After the call ends, the device registers again in LTE.
⚠️ Attention: Even if you have 4G turned on, without VoLTE support from the operator, the phone will be forced to switch to 3G when there is an incoming or outgoing call.
Some users mistakenly believe that the problem is a weak signal. In fact, even with an ideal signal level in the coverage area LTE, the absence of a voice gateway from the operator will force the phone to change its operating mode. This is the software logic of the modem, embedded in the communication specifications.
The role of VoLTE technology in preserving the Internet
The abbreviation VoLTE stands for Voice over LTE. This technology allows voice traffic to be transmitted directly through the fourth generation network, using the same channel as for the Internet. When VoLTE is active, your voice turns into data packets that go in parallel with the rest of the traffic.
Enabling this feature solves the problem of Internet disconnection radically. You can talk on the phone, download files, watch videos at the same time YouTube and use navigation without losing speed. The sound quality also increases, becoming clearer and more natural compared to regular calls.
For VoLTE to work, three conditions must be met simultaneously:
- 📱 Your smartphone must technically support this technology and have the appropriate firmware.
- 📡 Your telecom operator must support VoLTE in your region and on your base stations.
- 💳 Your tariff plan must include voice over LTE service (often it is enabled by default, but requires verification).
If at least one of the links in this chain is broken, the phone will return to the scenario CSFB. For example, you can buy a flagship smartphone with support for all frequencies, but if the SIM card is old or the tariff is outdated, the magic will not work. Operators are gradually introducing this technology, so in some remote areas it may not be available.
How to check and enable VoLTE on a smartphone
The first step in diagnosing the problem is to check the settings of your device. Manufacturers Androidof smartphones arrange the settings menu differently, but the general principle remains the same. You need to find the switch responsible for improving the quality of calls or working in networks LTE.
Usually the path to the desired setting is as follows: go to Settings, then select the section Mobile network or Connections. Inside, find the item associated with your SIM card. This is where the toggle switch Allow VoLTE or Calls via LTEshould be located. On some models, for example Xiaomi or Realme, this item may be hidden in the engineering menu.
If you cannot enable the function using the standard method, you can use the code to enter the engineering menu. Be careful when changing the settings in this section. Enter the command ##86583## or ##4636##on the dialing screen. In the menu that appears, find the section Phone Information and activate the switch VoLTE Carrier Provisioned.
☑️ Checking the VoLTE settings
After enabling the function, an indicator may appear in the status bar next to the network icon HD or VoLTE. This is a sure sign that the phone is ready to work in the new mode. However, if the icon appears, but the Internet still disappears, the problem may lie on the operator’s side.
⚠️ Attention: The engineering menu is intended for developers. Do not change other parameters in this section except those related to VoLTE, so as not to disrupt the operation of the radio module.
Influence of network mode and SIM card type
In addition to voice transmission technology, the selected preferred network type affects the stability of the connection. If the settings indicate the mode “Only 3G” or “Only 2G”, then the Internet during a call is out of the question, since these standards do not support simultaneous transmission. It is necessary to set the mode 4G/3G/2G (auto) or LTE/WCDMA/GSM.
It is also worth paying attention to the physical condition and type of your SIM card. Old large format SIM cards that were used 5-7 years ago may not support modern authentication protocols and VoLTE services. Telecom operators recommend replacing them with new cards of the format Nano-SIM or USIM.
Replacing a SIM card is a free procedure in the communication stores of most operators. The new card is guaranteed to support all current encryption and traffic routing technologies. Sometimes the problem is solved by simply moving the SIM card to another slot if your smartphone is dual-SIM.
| Network type | Voice support | Data support | Internet when calling |
|---|---|---|---|
| 2G (GSM) | Yes | Yes (GPRS/EDGE) | No (very slow) |
| 3G (UMTS) | Yes | Yes (HSPA) | No (switching) |
| 4G (LTE) without VoLTE | No (rollback required) | Yes | No (rollback to 3G) |
| 4G (LTE) with VoLTE | Yes (via data) | Yes | Yes (works) |
The table clearly shows that only presence VoLTE on the network LTE ensures continuous operation Internet. In all other cases, there is a break in the data session or a strong drop in speed to levels unsuitable for comfortable surfing.
If you have a dual-SIM phone, make sure that in the "Data transfer" settings you select the SIM card that has high-quality mobile data and VoLTE support.
Features of working in 5G networks
With the development of fifth generation networks (5G), the situation becomes even more interesting. In the architecture 5G SA (Standalone), voice is also transmitted through voice calls over a new radio interface (VoNR — Voice over New Radio). The principle is the same as VoLTE: voice and data go in parallel.
However, if the phone is in the coverage area 5G NSA (Non-Standalone), it uses the network core 4G. In this case, when making a call, the device will use mechanisms LTE. If VoLTE is not configured, the Internet will disappear again. Therefore, the presence of an icon 5G on the screen does not guarantee that the Internet will work during a call without the correct configuration of voice services.
It is worth noting that coverage 5G is still unstable in many regions. The phone may frequently switch between 5G, 4G and 3G. At moments of such switching during a call, short-term disconnections in the connection are possible. This is normal behavior of the device when searching for the most stable communication channel.
Why is 5G sometimes slower than 4G when making a call?
In NSA mode, the phone uses 5G only to increase the download speed, and the call is controlled through 4G. If the 4G signal is weak, the quality of communication and Internet may suffer, despite the 5G icon.
Third-party applications and workarounds
If it is not technically possible to enable VoLTE (for example, the operator does not support the service or the phone is not certified), you can use alternative communication methods. Applications for calling over the Internet, such as WhatsApp, Telegram, Viber or Skype, use exclusively the data channel.
When using such instant messengers, the Internet is not disconnected, since the call itself is Internet traffic. You can open websites and applications in parallel. The only negative is that the interlocutor must also have the application installed and access to the network.
There are also special VoLTE client applications for (root) users that can forcibly activate the hidden functions of the modem. However, using such methods requires in-depth knowledge and may lead to unstable operation of the phone or loss of warranty.
⚠️ Attention: Using unofficial patches to enable VoLTE may result in the phone no longer seeing the network or quickly running out of battery. Use such methods only at your own peril and risk.
For ordinary users, the most reliable way is to contact your telecom operator. Sometimes the VoLTE service is hidden in your personal account and you just need to activate it with a tick. After this, the phone can automatically pick up the new network settings.
The most reliable way to preserve the Internet when making a call is to activate the VoLTE service with the operator and enable the corresponding setting in the smartphone.
Diagnostics of problems with the telecom operator
Sometimes the phone settings are fine, the SIM card is new, but the Internet is still the same falls off. In this case, the problem may be on the base station side. Telecom operators constantly update equipment, and during the upgrade period some functions may not work correctly.
It is recommended to check that the access point settings are up to date. APN. Incorrect APN parameters may interfere with the correct routing of voice traffic through LTE. You can reset the settings to factory defaults in the menu Access points (APN) through the restore default settings menu.
It is also worth considering that some corporate tariffs or old archived plans may not include VoLTE support by default. In this case, you need to contact the operator's support service and clarify the possibility of connecting to a modern voice service.
⚠️ Attention: Network parameters and available services depend on the specific region and operator. Conditions may change, so always check the information in the official application of your operator or your personal account.
If all else fails, try testing another SIM card of the same operator in your phone. If the Internet works on another card, then the problem is in the profile of your main SIM card, and it needs to be reissued.
Frequently asked questions (FAQ)
Why does the 4G icon disappear as soon as I pick up the phone?
This means that your phone or operator does not support VoLTE technology. The device is forced to switch to the 3G or 2G network to make a voice call, since voice communication is not provided in the 4G network without VoLTE.
Does turning on airplane mode affect this problem?
Yes, in airplane mode all wireless interfaces are disabled. If you turn on only Wi-Fi in airplane mode, then calls over the cellular network will be impossible in principle. The Internet will only work via Wi-Fi, and calls are possible only through instant messengers.
Can VoLTE be enabled on any phone?
No. The phone must have an appropriate modem and software support. Budget models of previous years or phones imported from other regions (gray imports) may not have firmware profiles for local VoLTE operators.
Does VoLTE consume more traffic?
A voice call via VoLTE consumes Internet traffic, but operators usually do not charge it like regular Internet. Minutes are debited from the voice minutes package, not from gigabytes. Check this point in the tariff of your operator.
Why is there Internet on one phone and not on the other with one SIM card?
The difference is in phone models. One device supports VoLTE and has the correct settings, but the second does not. It is also possible that the “3G Only” mode is selected on the second phone in the mobile network settings.