To do that you are going to have to download and install another theme as Sprint has their logo in the top right of theirs. The other themes (all that I have seen so far) do not have the logo in the top right corner but rather the carrier name, which Cody's Personlizer will replace with the text of your choice.
Check out
www.thetouchblog.com and look at the TF3D themes and the TF3D Tool for changing them... and yes, they are all free.
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