Millions of O2 customers will have to go to 'no service' warnings today, following an overnight service outage.
An estimated 32 million people on the network have gone online with O2 blaming it on a software issue with a third party supplier.
The network issues started shortly after 5.30am this morning with their social media.
The company then issued a public statement confirming the network is down, adding it's working out the issue as quickly as possible.
O2, which has about 25 million UK customers, who said it was going to be online while out of the box.
To the best of our abilities, Giffgaff and Lycamobile customers, both subsidiaries of O2, are also affected by the equipment.
"We'd encourage our customers to use wifi wherever they apologize for the inconvenience caused," said an O2 spokesman.
One mother of two told Mirror Money she was unable to contact her children because of the outage.
She said she was receiving bouncebacks on the subject.
"I feel as if I've been cut off." "I use my phone to stay in touch with my children, and I do not know how to contact them."
O2 said that the problem is a third-party supplier, understood to be Ericsson, which has also affected other mobile operators around the world.
Ernest Doku, mobile expert at uSwitch.com, said: "O2 users will be concerned about this mobile data outage.
"While it is positive that voice calls are still up and running, it is likely to be a worrying situation for a large proportion of O2's some 32 million UK customers.
"Customers who are suffering can keep track of this incident using O2's own network.
"In the meantime, O2 customers can get in and out calls, but they will have to use WIFI if they want to get online."
In total, about 32 million mobile phone users have been affected including Tesco Mobile, Mobile Sky, Lycamobile and O2's Giffgaff.
So should you get your money back?
Regulator Ofcom said it's currently working with O2 to identify the root cause. In the meantime, we've identified your rights below.
"We are aware that O2 is experiencing problems with its network. We are in contact with the company to establish the cause of the problem, "an Ofcom spokeswoman told Mirror Money.
You can get updates on whether O2 is still down here.
Are you entitled to compensation?
Depending on the circumstances, it may be appropriate for your provider to provide you with some services. You can get this with O2 over the phone, online chat or on social media now, but be aware lines will be extremely busy.
In more extreme cases, where you need to take a closer look, you may be entitled to an additional refund or account credit.
In cases where you have been without service for some time, you may also have the right to the contract without penalty. There may be a term in your contract that you have said that your provider has failed in its obligations to you or breached a key condition.
Furthermore, if you're forced to incur any extra charges because of the outage, such as having to pay for public wifi, you can complain to your provider and ask for compensation.
How do I complain?
If your provider is failing to make a complaint, you may be unhappy with how long it is, you should follow their internal complaints procedure. You can get in touch with O2 here, it's worth waiting for the service to be back and running, first.
If you raise a question but it's still unresolved, you can submit your complaint to an independent Alternative Dispute Resolution (ADR) scheme after eight weeks.
If your problem is not resolved, ask your provider for a 'deadlock' letter that you can refer your dispute to the relevant ADR scheme directly before the eight week mark.
Ofcom has approved two ADR schemes – CISAS and Ombudsman Services: Communications.