iPhone 3GS from Att store

[jmandeluxe]

Hi everybody,
first I'm very new here.
second, I'm planing to buy an iPhone 3gs from a att store for $599. What do I have to do once I'm at home to make it work with any other provider like tmobile or so?
I searched everywhere for a walkthrough, couldnt find any though.
man i miss the times when i unlocked the 2g. was so much easier.
hope one of you experts can help.
thx

[Efrdman2008]

Why would you buy one from the store then unlock? once you buy it from the store you already are bound to a plan

[jmandeluxe]

You can buy without a contract for 599. but its still locked then.