Should be possible to do this on any device with access to the Engineering Screens. ... BlackBerry Bold forum
Should be possible to do this on any device with access to the Engineering Screens. See my signature for a link to my eScreen unlock code generator.
Engineering Screen>Mobile Network Engineering Screens>PLMN Selection...>
Select "Enabled RATs", and hit space until it just says "UTRAN".
Toggling WiFi power, opening the "Mobile Network Options" area in the general (non-engineering) device settings, and powercycling the device will reset it to UTRAN+GERAN (3G + 2G) or GERAN (2G only), depending on what you had selected in the "Mobile Network Options", prior to setting the base band value directly in the Engineering Screen.
As always, don't screw around with any other options in the Engineering Screens, unless you know what they do.