O2's mobile network has suffered from hours of outage preventing customers using their smartphones. Updated 10:49am 12/07/12.
The problems started yesterday afternoon at 1:30pm and is still affecting some users today. The failure has prevented scores of O2 users from making calls, sending text messages and using mobile internet.
O2 said: "We can confirm that our 2G network service has now been restored. Customers who were affected should now be able to make and receive calls."
"Our 3G service is starting to restore and customers should expect to see a gradual return of data services as the day progresses."
The problem also hit Giff Gaff and Tesco Mobile customers which both use O2's infrastructure. O2 is advising customers to switch their devices off and on in attempt to reconnect.
The mobile operator said the fault was related to one of its network systems but has not given any figures on how many of its 23 million customers were and still are affected. O2 has apologies for the inconvenience and confirmed all resources have been deployed to fully restore the service.
O2 has just tweeted saying it expects full service for all customers this afternoon.
We expect full service to return to all affected customers this afternoon. We'll continue to update— O2 in the UK (@O2) July 12, 2012