Apparent restriction

[Kaz59]

I am trying to phone out on numbers I have used countless times and I keep getting a message saying 'not registered to network', WHY!!!!!!!

[MI5]

@Kaz59 

Check your bills are paid https://mymobile.o2.co.uk/

Then check for network issues:

Guide: How can I sort out my network issues? 

Guide: Is the network down for me or everyone? 

Guide: How to find help & contact O2