hey guys i recently purchased an iphone 3g (singtel set) and read of all the horror stories of people getting an insanely high bills because of the EDGE and 3G feature being switched on all the time. i called up maxis and upgraded to the 3G unlimited plan for RM99 a month. is this the safe option so that i don't end up with a rm400 bill for my edge 3g usage? does this mean i can switch on all the features on my iphone and use as much or as little as i want for rm99 a month?

also my data roaming in the settings menu is switched off. should i leave the switch on or off? what does it do actually?