Sorry but I do not understand how you got this messed up.
The Sprint 30 day return policy is just that.
Did you keep the 1st phone for more then 30 days?
And you will get credit for the 1st phone, what reason could they possibly not give you credit for it? Are you not telling us something, like you used it to spread butter on your corn and BBQ on your pork? Took a swim with it because you thought it was a rubber ducky? (I need popcorn).
Sorry, but it sounds like you need to make some more calls, and get some credit for your problems, in the end, I would not think that it is worth it, and drop Sprint like a hot potato, I could not imagine going through your nightmare, and it sounds too much to me to be true, not saying it is not, but it is hard to imagine, something you are doing or asking for, maybe your wheeling and dealing, got you and Sprint all confused.
Best stick to the sticker price next time...