Is there a way to turn the phone network and leave wifi on?
Turn Airplane mode on then turn wifi back on.
A gun in the hand is better than a cop on the phone.
Only the Skilled Survive
A computer lets you make more mistakes faster than any invention in human history - with the possible exceptions of handguns and tequila.
Drill Sergeant Frick's Rules For Un-armed Combat.
1. Never be unarmed.
2. See Rule #1
USMC rule # 23 of gunfighting: Be polite, be professional, but have a plan to kill everyone you meet.
Another thing: Apparently, if you are just trying to turn off the 3G network, it happens automatically when the DX is connected to WiFi. If you are trying to disconnect from the phone signal, follow Backnblacks's advice above.