Wirelessly posted (8700g: BlackBerry8700/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)

With OS v. 4.2, go to options, then mobile network...

See help on blackberry for details. I think turning data off leave only phone and SMS. Browser, email, MMS etc...all data function disabled.