3 said it was the first operator in the UK to launch VoLTE, beating EE, the country’s largest operator, which had plans of commercially introducing the technology in the summer of 2015.

Dubbed “4G Super-Voice”, 3 said the service “is made possible by the addition of the low frequency [800 MHz] spectrum to the Three network, that will enable its 4G network to carry voice calls using VoLTE technology as well as texts and data.”

For now, the technology is only compatible with Samsung Galaxy S5 smartphones, with plans to add new devices regularly, including recent iPhone models later this year.

The operator claims 4G Super-Voice already covers 50 per cent of the UK population for indoor coverage as well as “more than three quarters of London, Edinburgh, Exeter and Birmingham”.

3 has also begun rolling out the technology in other cities including Cardiff, Manchester, Liverpool and Bristol.

By the end of the year it plans to reach 65 per cent of the population and predicts that it will have 5.5 million customers with access to 4G Super-Voice by 2017.

Roll-out of the service at a low frequency – 800 MHz spectrum – will allow mobile signals to travel much further into buildings and extend its reach to more rural areas, removing many of the current ‘blackspots’ across the country, 3 said.

Last year, 3 launched a Wi-Fi calling app called 3 inTouch that allows customers to talk and text using a WiFi connection and so improve its indoor coverage.

As for EE, last June it had planned a launch for early 2015, which was later pushed to the summer. It is still unclear when a commercial launch will take place. Mobile World Live is chasing up the operator to find out.