Thought I'd just put a question out there about how one might have 4/5 bars of signal + the 3g indicator, but still not be able to access the internet.

Basically when I'm coming home on the train, 99% of the time when I try and use my iPhone to access the internet whilst the train is stopped at Paekakariki, I'll have 4/5 bars of signal and the 3g indicator will be on. However doing anything internet related will result in it just spinning until about 1 minute north of Paekakariki when it comes to life.

I assumed that if you had 3g then you should be able to talk to the internet?