Have just bought a brand new iPhone 3GS last month, and have been running it perfectly on the XT network (prepaid) up until two weeks ago. I woke up one morning to find in the top left corner of the screen "No Service".
I reset the phone, reinstalled the carrier bundle and restored it completely. Nothing seemed to work. When searching the carrier settings, I found Vodafone NZ and 2 Degrees but no XT carrier.
As I bought it from Harvey Norman I took it in there, but they were clueless. They have had the phone for over a week now, and are saying they are trying to fix it themselves. Apparently if they cannot fix it, it is not covered by the warranty as Apple supply them only to Vodafone and it is clearly an XT network fault, so not their problem.
The technician thinks an Apple update has caused the problem, yet other XT iPhone users who have performed same updates are having no problems! Went to Telecom store and they were no help either. The phone is currently being help captive by Harvey Norman. Has anyone had the same problem and found a way to fix it? Would love to know, because if not, I have just wasted $1300 and am left without an iPhone according to Harvey Norman. Please help!