Hi there,
Are you able to confirm that roaming is enabled in the settings..? If it is what country have you travelled to..? In rare cases some providers don't have in-country agreements and data won't work. Or it could be that O2 has limited your service, or rather not enabled roaming for you. If you log-in to your account and check your tariff do you see something about an O2 Travel bolt-on..? If it's not there it 'could' explain why (so chat with O2 of course).
Jonty.
