This is horrible! I don't know much about credit reports but how much can this one bill really affect your ratings?? It's not like a mortgage or something, KWIM? I can't imagine it would do that much damage - but, like I said, I don't know a lot about how that works.
I feel SO bad for you.
Oh, I've heard that people who complain about co. on FB can get very fast results (or is that Twitter). I'm not on either, but have you been vocal on FB about your terrible treatment from Sprint??