Mobile network Three has apologised after customers across the country reported problems making and receiving voice calls.
More than 10,000 people have logged problems on outage site Downdetector, with the first issues reported around 1pm.
The network said a "small percentage" of customers were affected and that it was working hard to fix it.
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People on X reported problems in places such as Yorkshire, Derbyshire, North Lanarkshire and London.
"Six hours in and I still can't make or receive a call!" said user @nameisrichard.
"I'm trying to organise my mother's funeral and I can't make, or receive, a single call. It's appalling," said @flynn1965.
@bertis100 posted: "We have no coverage since 1pm in Motherwell Scotland."
The network first apologised this afternoon but said data and 999 calls were working as normal.
Three repeated the message at 7.30pm and said it was "really sorry" for the inconvenience.
However, its latest message only mentioned data services were unaffected, suggesting emergency calls might be impacted after all.
The firm's coverage checker is currently unavailable on its website.
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More than 5,000 people were still self-reporting problems on the Downdetector site just before 8pm.
It was announced last month that Three's merger with Vodafone had been approved, with the companies promising an improved service and an £11bn investment programme.
The merger is expected to formally complete during the first half of 2025.