O2’s internet service is down, leaving customers of the network unable to get online.
The problems mean those companies that share its network – such as GiffGaff and Tesco Mobile – are also being hit by the problems.
Calls can still be made by customers despite 4G data connections are broken, O2 said.
Affected phones, which may be every single device registered to the network, simply fail to show any kind of data connection and will not connect even when turned off and back on or when other workarounds are tried, according to users experiencing the problems.
Some users also suggested SMS messaging was not working, leaving them unable to send texts.
“Our technical teams are investigating reports of issues when using data,” O2 wrote on its status page. ”Voice calls are working OK. Our technical teams are investigating. We apologise for any inconvenience. Updates will be shared here as soon they are available.”
That page itself appeared to be having issues, often failing to load.
A tool on the same page that allows users to check if the outage is happening in their area did not appear to be working, bringing up an error message saying that the system was having “technical problems” but that “engineers have been notified”.
The problems were happening across the UK, according to the website Down Detector.
O2’s Twitter account spent the morning replying to users who were having issues with data. The messages made clear they were aware of the issues, said they were being fixed, and apologised for any problems caused.