Originally Posted by NJBlackBerry
Cingular BlackBerrys will work with AT&T or Cingular SIM cards (I have a Cingular 7290 with an AT&T Blue SIM card in it). But they are not unlocked.
Is your blackberry unlocked? Because as a sales rep, I have never been able to put a customers at&t sim in a cingular bb or phone for that matter. It displays a sim restricted message.
However, It could be possible for it to work.