Apparently the phone has some tricks up its sleeves with the help of Launcher Pro to allow forced roaming. These steps were posted by nfd77 on the sdx forum. I really love this phone.
"Instructions:
Make sure you are in LauncherPro.
Press: Menu -> Add -> Shortcuts -> Activites -> com.lge.LgHiddenMenu -> ServicesLG.
Name the activity whatever you would like, but "Hidden Menu" will do.
Open the activity you made.
Go to: CDG2 -> Field Tests -> Roam Preference.
Choose Roam Only.
*To disable force roaming follow the instructions but on step 6 choose Any.*
Enjoy!"
"Instructions:
Make sure you are in LauncherPro.
Press: Menu -> Add -> Shortcuts -> Activites -> com.lge.LgHiddenMenu -> ServicesLG.
Name the activity whatever you would like, but "Hidden Menu" will do.
Open the activity you made.
Go to: CDG2 -> Field Tests -> Roam Preference.
Choose Roam Only.
*To disable force roaming follow the instructions but on step 6 choose Any.*
Enjoy!"
