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, external, 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.