Fixing EDGE/3G/DT on iPhone 3G

Yes folks, I've pwned my iPhone again (for research.. of course) and now I got an iPhone 1generation with firmware 2.0 w/out Installer.app. After the easy way to jailbreak it, I've seen edge connection never goes down, and you know EDGE is pretty much expensive. So, how can we switch off the edge connection ? The first step was to search into

/System/Library/Carrier Bundles

Were you find all the carriers' directories. For instance inside the TIM_Italy.boundle there's interesting stuff like, for example:

Default_CARRIER_TIM.png FSO_CARRIER_TIM.png, Info.plist, ResourceRules.plist, carrier.plist version.plist .

So, the first thing that I've done was to rewrite the carrier.plist replacing the string apnXusernameXpassword with something fake. Nothing really happened . So, I tried by editing the personal configurations preferences present inside:
/var/preferences/SystemConfiguration/preferences.plist
typing vi /var/preferences/SystemConfiguration/preferences.plist . Now, searching the string apn (/apn) I've found two different places where it's possible edit it !

The first one :

The second one:

I changed the default value af APN string from "1" to "0", blocking the Edge access by default. So far I'm not sure which is the default "apn-key" and which is the user "apn-key", so I've just replaced both . It's working well !!

Enjoy the tip.