Users of O2 across the UK are facing network problems this morning while 4G services and data have stopped working.
The affected phones are simply unable to show any data connection.
O2, one of Britain's largest mobile networks, has posted on its website: "Our technical teams are examining reports related to issues during data usage, and voice calls work properly.
"We apologize for any inconvenience, updates will be shared here as soon as they become available."
Companies like Tesco Mobile and GiffGaff, which share the O2 network, are also experiencing problems, as well as services such as Transport for London's electronic timetable at bus stops.
TfL tweeted: "There are reports that live bus updates to our Countdown systems have declined.The company that updates data on our Countdown Systems network is currently having trouble providing this service.This problem has been studied."
Network problems seem to have started at 5 am, with thousands of customers reporting interruptions.
It is not clear when the problems will be solved.
Furious customers have vented their frustration on social media.
A Twitter user wrote: "Network O2? Down? Really? !!!!!! @ O2 scary cover all the time anyway, I do not see the time to turn off my service provider."
"This is ridiculous apparently it's the whole country I can not rely only on the wifi network," added another.
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