Changing the Sprint banner is just one of many ways to personalize your rooted HTC EVO. Some custom ROMs and apps make editing the banner very easy, but what if you don't have root?
The process is a little more complicated but thanks to slayer69's fantastic tutorial, which you'll find at the xda-developers link below, it can still be done within minutes. Best of all, you don't even need root to do it on your HTC EVO 3D. All you need is your unique MSL number (which you can get from Sprint with no questions asked), a copy of Qualcomm Product Support Tools (better known as QPST) installed on your computer, and the ability to follow directions, particularly if you run into driver issues. You'll need your EVO 3D and USB cable too, of course, but that kind of goes without saying.
This may work on the EVO 4G as well, but I can't confirm it since mine is beyond dead (Qualcomm hardware error code and all) and it was rooted while it was alive anyway.[xda-developers]