A friend loaned me this phone to try out Windows Phone 8. I'm on Telecom prepay. When I put my SIM in the phone, it worked fine - texts, calls and internet. I was at work at the time in Wellington CBD. When I went home (Whitby) I noticed I had "no service". Strange, but I had Wifi and didn't worry too much about it - I tried pulling the battery and refitting the SIM - no change, left it at that.

But then, when I got to work the next day I found it was working again. That night on the train, after coming out of the tunnel near Takapu Rd - no service again.

Today back at work, it's all fine.

APN settings are fine. Any ideas?