How do i get a sidekick 3 to work with at&t/cingular?

So im buying a sidekick 3, i already know that i have to unlock it. Well i was doing some reading and i read that it only works for calling if you have at&t/cingular [which i do] well then i read that i can call at&t/cingular customer service and they can do something where i can text too. If someone can tell me what i need to do, like what i need to ask, that would help me a lot!
Thanks!

Did your sidekick is lcoked with any carrier ? If so, use unlock code to unlock it . You can get it from any of the online vendors like OnlineGSMUnlock.com to unlock it .