Here is the thing, you can unlock your phone but in needs to have the right radio frequency as the networking your trying to connect to,
Example would be AT&T phones run on GSM so an AT&T phone would work with Simply Mobile; Sprint uses CDMA so a Sprint phone that's unlocked will work for another carrier who runs on a CDMA frequency...
Here is a list of CDMA and GSM carriers:
http://en.wikipedia.org/wiki/List_of_Uni..._providers
Here is a CDMA cracking program:
http://www.cdma-ware.com/workshop.html
This tool is rather a reprogramming tool for the phone it's self change the serial number whatever it lets you do.
If your looking to just jailbreak or root the device it's best to do your homework for the different updates will cause problems for old jailbreaking programs, make sure you just follow the steps on how to root or Jailbreak the device.
My best work was I changed my Iphone 3GS to have the Android OS ;) (well the ability to use Android products, make it look like a droid, and act like a droid) but it still was the iOS from apple.
Cell Phone can be a lot of fun.