My dad gave me his iphone 3gs, its jailbroken and unlocked. Nice device, would like to use it.
I'm currently using a BB Curve 8520, which i've had on orange UK contract for 7 months now.
On my bills I have :-

Orange Mobile internet data
Orange BlackBerry data

I was advised to download an APN changer for iphone and put the "orangeinternet" apn in iphone, and it would be good to go.
So what im wondering really, is if I use the iphone with my BB sim in, will the data charges come from the
Orange Mobile internet data ?

I wont get extra charges will I?

Thanks in advance.