Well here is how.
This is a rough guide, maybe I'll get ambitious and spruce it up when I have some more time...
Install HTC Sync if you haven't already..
Get it here.
Gonna need the HTC Diag drivers, least I did... these work fine:
http://rapidshare.com/files/29352942...AG_Drivers.zip x86 32bit
Here are the /64 bit drivers thanks to techwerkz
Mod edit: No linking to warez site or suggesting users to get warez is allowed
Enter DIAG mode, dial ##diag#, let windows install the drivers...most likely it won't find the HTC DIAG drivers, but they are in the link above... get it installed.
Now in CDMA workshop, you really don't want to be effin' with stuff you aren't sure what it is... but we are here to change the banner right? riight so don't be changing anything else and you'll be a-ok.
Select your port, hit connect, hit read... goto the NAM tab...hit Read ...change the Banner from "Sprint" to whatever..hit "Write".... then you can reboot the phone and its done.
To find your port...
Select your port, hit connect then hit read. ( picture shows "Disconnect" only because I already pushed connect... )
Goto the NAM tab, hit read, change the banner, hit write. Reboot your phone
Mods if there is a problem with me posting the link to isohunt, I'll gladly remove it.