i did a debrand of 8520,its really simple,,,
just delete the vendor.xml.
then flash with desktop manager.
but say no to backup configeration,it warn you bout reregister with blackberry,but just carry on,when finished,,,it was unbranded
it was a unlocked blackberry 8520 with t-mobile uk branding,i downloaded the uptodate t-mobile flash,deleted the vendor,choose not to backup,flash+its unbranded.....
hope it helps