Wirelessly posted (HTC Diamond: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.11) Sprint MP6950SP)
Unlocking just allows you to flash a custom rom or radio to your device not switch carriers at will. You have a cdma phone and you are thinking of SIM Unlocking which is for gsm devices which allows you to use any gsm carrier you want. The only way you can switch carriers with a cdma device (legally) is contact the carrier you want to use and see if they will add your phones esn to their network which allows you to make/receive calls on their network. That can be difficult.
Sorry to burst your bubble.