on 27-12-2013 14:41
Ensure your handset is unlocked or locked to the 02 network in order for a giffgaff sim to work. try the sim in another handset. if your handset is locked to another network best bet would be to pop down to your local mobile shop they should be able to unlock for a small fee, for more info follow the link below to the giffgaff unlockapedia.http://giffgaff.com/unlock
on 27-12-2013 14:46
Are you able to try a gg sim in another unlocked or o2 phone ? This would eliminate the sim as a problem.
You say the phone was bought as an unlocked phone ? Did you buy it second hand ?