Subscribers to Vodafone’s UK mobile network have had problems making and receiving calls.
While the issue prevented voice calls connecting, customers were still able to text and use mobile data.
According to Downdetector, the problem began shortly after 17:00 BST and affected people across the country.
A spokeswoman for Vodafone said a fix had been made at 18:10 BST and that its operations had “started recovering” shortly afterwards.
She added that not all Vodafone’s users had been affected.
Earlier the firm had told the BBC that the incident had impacted “a large number of customers”.
“I understand it’s particularly inconvenient, especially in a lockdown situation,” a spokesman added.
The company said the problem had been caused by a change it had made to block a range of telephone numbers used to make spam calls.
“Somehow that had a knock-on effect to the voice platform,” it explained.