Not Registered On Network

[JeffO]

On booting up, my new phone into which I have carefully slotted my Sim Card keeps showing Not Registered On Network and prevents me from accessing the service. What has gone wrong?

[jonsie]

We’re just customers like you but it sounds like you’ll need someone to access your account which can’t be done from here. If you message O2 using the links below, they should be able to help you with this
or give them a call on 202  or 0344 809 0202

Guide: How to find help & contact O2 

Guide: How can I sort out my network issues? 

Guide: Is the network down for me or everyone?