Two very good detailed explanations of how to do the removal of the carriers id.
READ both to fully understand what is needed depending on your needs.
The links below are for older models but the reload for the OS from another carrier will still involve some of the items mentioned. READ before doing anything.
http://www.blackberryforums.com/gene...-t-mobile.html
http://www.blackberryforums.com/blac...-xml-file.html