I was out and about around Palmerston North today so was jumping in and out of 2Degrees, with its associated loss of data availability as I moved around town. Once I got home my phone was back on 2Degrees and working fine. I put it down in my office. Next time I looked at it, a couple of hours later, the phone was back on 3G and was roaming.
I restarted the phone and manually set the network - back came 2Degrees. Next time I look at it its back to roaming.
This has happened all in the same room of the house without the phone being moved more than the distance from my desk to my ear.
Often, when moving around town, I have to set the phone to flight mode then back in order to get back onto 2Degrees but I've never before experienced it switching over to roaming at my home. My home is well within the zone.
Any idea what could be causing this?