VoLTE in Phones - VoLTEsim

Quick answer

Every smartphone sold in the UK since approximately 2018 supports VoLTE in hardware. Activation requires a VoLTE-provisioned SIM, a compatible handset on the carrier’s approved device list, and VoLTE enabled in the device settings. On Android: Settings > Network > Mobile Network > VoLTE. On iPhone: Settings > Mobile Data > Voice and Data > VoLTE.

Hardware requirements

VoLTE requires an LTE modem chipset with IMS stack firmware. All major chipset families – Qualcomm Snapdragon, MediaTek Dimensity, Apple A-series – have supported VoLTE since 2015. The VoLTE capability in a handset consists of:

LTE modem with QCI 1 GBR bearer support
IMS client firmware (handles SIP REGISTER, INVITE, and media negotiation)
AMR-WB codec support in the audio stack
Operator-specific VoLTE configuration files (often delivered via OTA update or carrier bundle)

Carrier approval

UK operators maintain approved device lists for VoLTE. A handset must be certified by the operator – tested against their specific IMS implementation – before VoLTE is activated on that combination of device and network. Handsets sold through operator channels are pre-approved. Some unlocked or parallel-import handsets may not appear on the approval list, and VoLTE may fail to activate even if the hardware supports it.

Handset source	VoLTE likelihood	Notes
Bought from UK operator	High – pre-approved	Configuration usually automatic
Bought from UK retailer (unlocked)	High for major brands	Apple, Samsung, Google usually approved
Imported / grey market	Variable	May lack operator-specific VoLTE config
Older handset (pre-2017)	Variable	May need firmware update; some not approved

Enabling VoLTE

On most devices VoLTE activates automatically when a compatible SIM is inserted. If it does not activate automatically:

Android (general path): Settings > Connections (or Network and Internet) > Mobile Networks > select SIM > Advanced > VoLTE calls (toggle on)

Samsung Galaxy: Settings > Connections > Mobile Networks > VoLTE calls

iPhone: Settings > Mobile Data > Mobile Data Options > Voice and Data > select VoLTE (or 5G/4G depending on model)

The exact menu path varies by OEM and Android version. If the VoLTE option does not appear, the handset either lacks carrier approval or the SIM is not provisioned for VoLTE.

How to confirm VoLTE is active

During an active call, the status bar shows “HD” or “VoLTE” indicator on most Android devices
On iPhone, the call quality label shows “HD” for AMR-WB calls
Call setup time is noticeably faster than CSFB (under 2 seconds vs 6-8)
On Android, engineering mode (*#*#4636#*#* on some devices) shows active bearer type during a call – QCI 1 confirms VoLTE
The data icon does not change or disappear during a call – data connection stays on 4G

VoLTE and Wi-Fi Calling

VoWiFi (Wi-Fi Calling) uses the same IMS infrastructure as VoLTE but carries the SIP and RTP traffic over a WiFi connection via an IPsec tunnel to the operator’s P-GW. VoWiFi requires the same ISIM credentials and IMS provisioning as VoLTE. It is useful in buildings with weak cellular signal but good WiFi coverage.

For devices that need reliable voice in locations with poor LTE coverage, VoWiFi via a WiFi network is a valid alternative – provided the SIM is provisioned for both VoLTE and VoWiFi.