EE is having network issues this morning, with hundreds of customers claiming they are unable to make or receive calls.
The mobile network has been having issues since 08:32 this morning, according to data from website DownDetector, which monitors online outages.
The issue is primarily affecting users in London, Glasgow and Leeds, according to DownDetector's live outage map.
Most of the complaints relate to a lack of mobile internet or mobile network.
However, the issue doesn't affect everyone – Mirror Online has verified that EE still works on some phones.
EE customers have flocked to Twitter to complain about the being unable to access the network.
EE has not officially commented on the outage, but is advising customers to switch their phones off and on again via its official Twitter account.
As a temporary fix, if you have access to WiFi, you can enable WiFi calling on your phone, which will allow you to make and receive calls.
Commenting on the news, Ru Bhikha, mobiles expert at uSwitch.com, said the outage has the potential to affect a huge number of people.
“Our reliance on our mobile phones for all manner of things in our work and social lives makes even the shortest amount of time without reception a stressful and damaging one, and it is concerning that EE has not yet identified the cause of the problem," he said.
"EE is generally highly regarded for its reliability, consistently ranking low in Ofcom’s complaints data, and we all accept that things can go wrong - it is how networks respond that is the real test.
"EE needs to get on the front foot quickly, or risk customers frustration growing among its large customer base."
