Three is the first network in the UK to enable VoLTE (voice over LTE), promising its customers they will be able to us their phones "in more places than ever before".
It's hard to say this stage what sort of first-mover advantages Three will enjoy, but it is confident they will prove to be substantial, with over a million of its customers expected to have a VoLTE-enabled handset by the end of the year, according to the operator.
By making it possible for customers to make calls and send messages over the 4G network, Three can offer a better performance in some low-reception areas, as well as better connection indoors.
The Maidenhead-based firm, a subsidiary of Hutchison Whampoa, also announced the roll-out of its 800 MHz spectrum which will facilitate its new '4G Super Voice' service, meaning penetration in hard-to-reach places should be better.
"Not being able to use your phone as and when you want, no matter where you are, is one of the biggest pain points for customers," said Danny Dixon, director of customer strategy at Three.
"Today's announcement is the latest step in our efforts to offer customers a quality experience on what is already the UK's most reliable network."
Three failed to touch on what the new service will mean for HD voice, Wi-Fi calling handover, uninterrupted 4G, etc. – but confirmed that it will be available on the Samsung Galaxy S5 from launch, as well as the new iPhone.
The launch of Three's 4G Super Voice service came only a few days after one of its rivals, Vodafone, announced it had enabled Wi-Fi calling on its UK mobile network.
"It works wherever a customer is connected to Wi-Fi, in a café, at home or the office, and automatically connects just like a normal call when a mobile signal is weak or non-existent," explained Vodafone UK consumer director Cindy Rose.