Telecoms firm JT has confirmed it intends to begin the phased switch-off of its 3G mobile network across the Channel Islands from January 2025.
JT said while 3G had supported calls and data for nearly 20 years, the vast majority of users now used other mobile technologies.
A UK-wide shutdown of 3G is expected in 2024 but customers with older devices will no longer be able to access most of their mobile data services.
Sure and Airtel-Vodaphone, the other two providers in the islands, have not made announcements on the subject.
JT said that its 3G network carried a monthly average of approximately 5% of user data traffic, which was declining.
The company said the move would help it to reduce its carbon footprint because 4G and 5G were more energy efficient.
It said over the next year it would "guide customers without modern handsets onto the right device for them".