Thanks for your reply.
I flew into Spain from Ireland. My phone connected to local carriers for the first day or so and I was able to use my call credit, 3G etc. Then 'NO SERVICE' appeared and the phone has been struggling to connect to a carrier ever since. Every few hours it shows, say 'MOVISTAR' or 'TELEFONICA' but quickly reverts to NO SERVICE.
Frustrating as battery is running down. I have to put phone on Airplane mode.
You didn't say what membership you're on.
I presume you're on Guido.
Could be this problem due to the stupid way that Apple do things.
Hope this helps.