if you mean unlock to use on a different carrier, where are you currently? its possible youre allready unlocked.
if your locked to t mobile,or some other regional carrier,there are a couple ways to unlock:
-call your carrier and ask for an unlock code. if you have an account in good standing,they may give it to you(i know att will,if youre in good standing for 60+ days. other carriers are prolly similar)
-root,s-off,then use a "DIAG" file(can be dangerous if youre not careful)
-pay for an unlock code.
yeah,it sucks to part with your hard-earned $$,but if youre carrier will not release an unlock code,its defiantely the fastest,easiest way