On the T-Mobile Network, to unlock the Samsung SGH-T919 (Behold):
*The 8 digit code can be obtained by calling T-Mobile Technical Support and given the representative the IMEI number. In exchange they will give you the Subsidy Unlock Code.
To obtain the IMEI number press *#06# on your mobile device. The IMEI number is the first 15 digits.
Follow this link to see instructions about configuring your unlocked device for Web, IM, Java, and MMS settings.