Virgin Media O2 begins switching off one of its mobile services this month, which could leave some customers with no data access.
The UK's major mobile providers, including EE and Vodafone, have gradually been axing all 3G services over the past few years.
Virgin Media O2 will now become the latest provider to switch off its 3G network so it can focus on the "faster, more reliable and more energy-efficient" 4G and 5G networks.
It's 3G network switch off begins in April, with the city of Durham the first area affected.
Virgin Media O2’s Chief Technology Officer, Jeanie York, said: “Switching off 3G will be an important milestone in the evolution of our network, enabling us to focus our attention and investment on faster and more reliable 4G and 5G networks that will deliver improved services for our customers.
“By starting in just one location and by putting careful monitoring in place, we’ll minimise disruption to customers and ensure the success of this essential modernisation programme.
“While the vast majority of our customers already have a 4G or 5G device and will not be impacted, our priority is to provide support to those who need it.
"That is why we are reaching out directly to customers who do not have a 4G or 5G-ready device, and calling those we know are vulnerable, to help them prepare.
“We will continue to support our customers as we complete the switch off of our 3G network.”