We haven’t tested this (as I don’t want my Blackjack in GSM only mode), but if you are in a Cingular non-3G area and want to save on battery life, you can try this to keep your phone in GSM/EDGE only mode.
1. Enter *#1546792*#
2. Select Option 3 (Network and Call Settings)
3. Select option 5 (Network Mode)
4. Select GSM
If anyone decides to give this a shot, let us know how it goes.

