Hi,
The usual methods of assistance are ;
Remove your sim card and wipe it down to remove any static build up.
Go into the phones settings and manually choose the 02 network.
Check here to ensure your local masts are working fine http://status.o2.co.uk/
If you feel their may still be an issue with the mast then still give 02 a call to challenge the mast status.
Phone 02 to ensure your account is set up correctly.
Try your sim in another phone to rule out if your brothers phone is faulty.
Replace the sim card by picking one up at your local 02 store or ask for one to be posted to you by ringing 02 on 202{contract} or 4445{payg.}
They will action the swap instore for you or you can do this at home http://swapmysim.o2.co.uk/
