I believe that after a given period of time they are required to give you an
unlock code to allow you open your phone up for any service provider that fits.
(In this case GSM) you can then subscribe to a service and put in the SIM card.
I think that you should be able to use any hardware present service within the
phone without a problem.
ATT and TMo use different frequencies for 3G. Euro iPhone might work on
Tmo 3G, but US iPhone won't.
*************************************************************************
** List info, subscription management, list rules, archives, privacy **
** policy, calmness, a member map, and more at http://www.cguys.org/ **
*************************************************************************
