O2's internet service has gone down this morning, leaving people with phones on the network unable to access the internet.
The network confirmed on Twitter that its users are 'unable to access data services' and 4G coverage due to a massive data failure.
Their technical teams are working on the issue as a 'high priority' and updates will be given throughout the day.
Providers such as Tesco Mobile and Giffgaff, which use O2's network, are also affected.
Customers can still make calls but cannot use applications that rely on a data connection or browse the internet.
Some reported being unable to send SMS messages, although this is unconfirmed.
Others complained of having to drive without being able to access the satnav function on their phones, while some even demanded refunds from O2.
The problems are UK-wide and O2's Twitter account spent the morning engaging with customers who were having issues with data.