I just realized tonight why my internet usage billing on the iPhone seems excessive compared to, say, when I was using my Nokia XpressMusic 5800. I’ve seen a lot of complaints on the internet about such incidents and contrary to what many are suspecting it is most probably NOT the telecom carrier’s sneakiness/dishonesty, nor is it exactly the iPhone hardware’s fault.
The most likely reason you are getting billed for internet usage that you don’t believe you’re using is actually rather simple but easily overlooked, and it is: ADVERTISEMENT SERVED BY FREE APPS! Whenever an application shows an ad it loads it from the net and if you do not have wifi turned on, it will do a data connect using either 3G or GPRS (so turning off 3G will not help). One way to make sure you don’t connect is to just stick an invalid Access Point Name (APN) in Settings -> General -> Network -> Cellular Data Network. If you have SBSettings, you can enable toggling of 3G and EDGE and toggle both off which is a more elegant of turning your data connection off as well as making it faster to turn on as well.