on 13-02-2015 11:34
on 13-02-2015 11:34
on 13-02-2015 11:39
on 13-02-2015 11:40
It could be a number of things.
Check netrwork coverage for problems in your area here : Service Status
Try cleaning the simcard and rebooting the phone.
Or have the sim replaced at your local O2 store.