The ONSIM Network

What is VoLTE and why does it matter?

VoLTE stands for 'Voice over Long-Term Evolution' and it's the process of making voice calls over a 4G network rather than making calls over older packet-switched (2G/3G) services.

Calls made over VoLTE are of a much higher quality, offer quicker call setup times and allow the use of voice and 4G data services on devices simultaneously.

ONSIM fully supports VoLTE calls on it's network on supported devices.

What are the benefits of VoLTE?

Better Quality Calls

VoLTE often provides superior voice quality compared to older technologies, thanks to the use of higher-quality codecs and the ability to utilize wider bandwidth. This results in far superior 'High Definition' voice quality when making and receiving calls.

Improved User Experience

Users can enjoy uninterrupted access to high-speed data services while on a voice call, enhancing their overall experience and productivity.

Faster Call Setup

VoLTE typically offers faster call setup times compared to traditional circuit-switched voice calls, leading to quicker connections. If you remember making calls via 2G or 3G there would be a delay (often 5-10 seconds or so) before outgoing calls would connect. With VoLTE calling there is no delay and calls should route almost instantly. This is great if you have a ONSIM and paired IP Phone as they will ring simultaneously without any delays.

Efficient Use of Network Resources

VoLTE allows operators to make more efficient use of their LTE networks by using a single network for both voice and data services, which can result in better network performance and capacity utilisation.

Energy Efficiency

By using a single 4G network for voice and data that is more energy efficient and deprecating older technology (2G/3G), networks are able to reduce their energy consumption significantly. Estimates over the recent switch-off of 3G network services by UK mobile operators estimated that they would reduce their overall energy consumption by around 20% by removing the older 3G network infrastructure.

Simultaneous 4G Data

Before VoLTE, when a device was connected to a 4G or 5G data network it would need to 'drop-down' to 3G or even 2G in order to facilitate a call. This not only resulted in a slow call setup time (due to the registration/de-registration procedure) but also limited data capabilities to 3G/2G speeds whilst on the call. This interruption in data service during a voice call was inconvenient, especially in situations where you may need to access data services while on a call, such as checking emails, browsing the web, or using apps. With VoLTE, voice calls are transmitted over the LTE network, which means that data can still be transmitted over the 4G network simultaneously. This enables a more seamless experience for users, allowing them to continue using high-speed data services while engaged in a voice call without any interruption or degradation in data performance.

Requirements for VoLTE-calls with ONSIM

All our plans fully support VoLTE. That being said, you will need a smartphone that supports VoLTE calls that is supported on the ONSIM network. You can find an overview of compatible, supported devices listed below.


Apple has introduced support for ONSIM beginning with iOS 15.4.

  • iOS 15.4 or later. Recommended: iOS 17.1 or later
  • iPhone XR or later. iPhone 12 or later is recommended when ONSIM is used as a second SIM
  • Supported on US and Global iPhone models only
  • eSIMs supported
Known Issues
  • VoLTE Must be manually Enabled


Samsung has introduced support for ONSIM across several device classes running Android 13 and OneUI 5.1.

  • Android 13 + OneUI 5.1
  • Supported on US and European models only
  • Please visit Samsung’s website for eSIM support information per device
Known Issues
  • None

Google Pixel

Google has introduced support for ONSIM on Pixel devices starting with Android 13 March 2023 update.

  • Android 13 with March 2023 update or later
  • Pixel 6 and later
  • eSIMs supported
Known Issues
  • Pixel 6a and 7a are not recommended for international roamers


What is VoLTE?

VoLTE, short for Voice over Long-Term Evolution or Voice over LTE, is 4G calling (Making voice calls over the advanced LTE/4G mobile network infrastructure rather than older 2G/3G services).

How can I tell I'm using VoLTE

When making a call the network indicator will remain on 4G or LTE rather than displaying 3G/E/G.

Does VoLTE cost more?

No - there are no additional costs of using VoLTE on the ONSIM network.

Is VoLTE the same as VoIP?

No - although both use data to transmit voice calls VoLTE is prioritised on the network and offers far superior quality, security and reliability.

Does making a VoLTE call use my data allowance?

No - on the ONSIM network making a VoLTE call does not use your data allowance.

What's the difference between LTE and 4G?

Nothing - they are two names for the same technology

Is VoLTE secure?

Yes - calls via VoLTE are encrypted and more secure than older calling technologies.

Should VoLTE be on or off?

ON - VoLTE can greatly improve the quality & reliability of calls especially as UK networks switch off older 2G & 3G services.

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