Mobile operator O2 was left red-faced after thousands of customers lost signal across the UK on bank holiday Monday.
The company was told to "sort it out" by Business Secretary Sajid Javid, who took to Twitter along with hundreds of others to criticise the service.
After several hours of downtime, the network for affected customers in London, Manchester, Glasgow and Northern Ireland was back online at 11.35pm yesterday.
O2 blamed phone mast issues around the UK for the problem, adding: "We apologise for any inconvenience caused to those customers affected and we will now begin a full investigation to identify the root cause."
While Cabinet minister Javid had tweeted "No signal @O2. Please sort it out", telecoms expert Dan Howdle said it was unlikely that angry customers venting on Twitter would actually switch providers.
The editor-in-chief of Cable.co.uk said: "As infuriating as it may be during the disruption, I would be very surprised if many jump ship from O2 as a result."
He pointed to his own research of 2,500 UK mobile users, which found 50 per cent are still with the same provider they signed up with years ago.
Howdle added that instead of just venting frustrations on social media, customers should be prepared to move for better service.
"If reliability is our number one consideration, as many O2 users affected by the outage now claim, we must be prepared to vote with our feet," he said.
O2 is in the process of being bought by Three owner Hutchinson for 10.25 billion.
Three itself suffered an outage in Ireland last month.
