As Raptor464 said, it is the Vendor ID which enables/disables the ability to manually switch between 2G and 3G.
And as mentioned above, there are two reasons why someone might want to debrand an AT&T phone and continue to use it on AT&T's network:
1) The option to manually switch between 2G and 3G.
2) The ability to change the Voice codec for phone calls.
1) Requires a VSM with a VendorID that allows manual 2G/3G switching to be loaded on the phone. AT&T seems to require their own VendorID (102) in order to log into AT&T hotspots so this means that manual 2G/3G switching and AT&T hotspots are not compatible.
2) Requires a VSM with the Engineering Screen code embedded. By manually editing a VSM you can get the AT&T VendorID (needed for hotspots) and the Engineering Screen code. This means that voice codec switching and AT&T hotspots are compatible.
|