The Sony Ericsson GAIT phone, the T62U, can be adjusted a little by the user. Enter *777* and reboot your cell phone. When it comes back on it will show a letter for the system you are using (G=GSM, T=TDMA, A=AMPS).
You can now go to the menu>settings>networks and then change things like your Protocol Stack (for if you want your cell phone to seek GSM only, act as primarily a TDMA phone, etc...). Reboot phone for this to take effect.
You can also go to SID/SOC and disable this list, but that can get costly.
For disabling these features: Menu>Extras>Debug Tools>Advanced Debug>Off. Then reboot your phone.
The main reason for not resetting your Protocol stack is that it may bypass some features in the the GSM chip. While I have not heard for sure on this one it seems that this may create some problems when you are changing your plan (say like going national instead of local). Does anyone know if this is really a problem?
AT&T users may have to set up their TDMA portion before that GAIT feature works properly. See your dealer.