Hi guys, 

This has happened to me a few times now on this trip and I just realised why. 

My iPhone upgraded to the newer build of iOS while I'm overseas with the roaming switched off. 

I believe that every time it does update, and that iMessage needs to re-authenticate - it will incur a roaming cost. 

So been a costly software update.

I messaged 2degrees about this about 4 days ago and they have not replied.