Millions of Three customers have been unable to use their mobile phones since Wednesday night, after a network meltdown left them without a signal or access to data.
The company, which has about 10 million customers in the UK, said: “Three is currently experiencing technical difficulties with our services across voice, text and data which means that some customers will be experiencing an intermittent service.
“Our engineers are working on the issue now to fix the problem as soon as possible. We are sorry for the inconvenience caused to our customers.”
Downdetector, a website that tracks outages across various networks, said the problems started at 11:28pm BST on Wednesday.
It has received 8,507 reports of problems, mainly from users in Manchester, London, Glasgow, Birmingham, Leeds, Liverpool, Nottingham, Edinburgh, Bradford and Sheffield.
The Three website, which was also down, posted a message on a static page that said: “We’re doing some essential maintenance on the site, and we’ll be back up and running soon.”
Many Three mobile users complained they had been unable to make calls or go online for hours and that there had been no communication from the company.
After a long silence, Three tweeted on Thursday morning:
Adam French, a consumer rights exper at Which?, said: “Huge numbers of Three customers have woken up to find they are unable to make calls or use roaming data and will be left feeling angry and frustrated as a result.
“The mobile operator has to do right by its customers by keeping them informed, ensuring no one is left out of pocket and we expect those affected by this lengthy lack of service to be compensated.
“The UK is already lagging behind the rest of the world on the provision of 4G. Failures like this will only intensify the pressure on the government, industry and the regulator to up their game and ensure we get a decent service.”