Is it normal for my phone to say sprint?

That's why. Its a sprint ROM. The eri.xml file has sprint coded into it Flash a sprint or VM rom. I believe it changes from ROM to ROM.

 

So... Is there a way to change/customize that Sprint tag?

 

It's not foolproof, but when the "VM leak RUU" came out in May the Evo 3D developers were working to "Sprintify" the Virgin Mobile parameters in that ROM and used tools like Agent Ransack to search the contents of the unzipped ROM file to find the references to "Virgin". That won't find all the things that are different, but if you search for "Sprint" it will probably at least point out the places where changes need to be made.

Perhaps one of the developers here has a guide for what needs to be changed to modify a Sprint ROM to VM, but unless something like that is available searching the unzipped ROM is a good place to start.

ramjet73