Vodafone customers say they are struggling to make calls, seemingly after technical issues at the network.
Users said they were experiencing an array of unusual problems. Some said they were able to call other people on Vodafone – but not speak to people on other networks, for instance.
Data connections appeared to be working as normal, however.
On Twitter, Vodafone responded to affected users by apologising and asking for more information. It encouraged affected users to check its online service checker – which indicated there were problems in some areas.
The company did not immediately respond to a request for comment.
Tracking website Down Detector also showed problems at Vodafone, starting on Monday afternoon. Other networks were also flagged as having issues – but that may be simply because Vodafone calls to those on other providers were failing to connect.