O2 customers have found themselves unable to make calls because of apparent issues with the phone network.
Over the morning, a number of people on the network have said they are unable to phone anyone else.
Users reported that they appeared to have full bars – and that other parts of the network were ringing – but that their phone simply wouldn't ring out to other numbers.
Normal fixes such as switching off the cellular connection or restarting the phone entirely did not seem to work.
O2's network status page recognised the issues but gave little information on what they were being caused by or when they might be fixed.
"We’re aware of an issue in some parts of the country," a message on its official website read. "Our technical teams are investigating.
"We apologise for any inconvenience."
The official O2 account also spent the morning replying to affected users to apologise for the outage.
Though O2's statement said the problem was "in some parts of the country" outage tracking website Down Detector showed issues across the UK.
