Sprint's upgrade eligibility and customer-retention

[Chief85]

We recently had to switch over from our old legacy plan with 7 lines on it because one of the lines wanted to get a Pre. So of course, we had to get TWO plans because you can only put 5 lines on a plan. Needless to say, this was not a happy discovery. We did it anyway, and yesterday I called and got transferred to customer retention because I said the magic words ("verizon or at&t") to express my displeasure. I indicated that I would be placated if I received upgrade eligibility on my line, which wouldn't be eligible for the full thing for another 1.5 years. I was told by a couple reps that this was literally impossible to do. I persisted and yelled a bit, but they wouldn't budge. Eventually I had to leave the office so I hung up on them.

Is it worth pushing this further? Or is it literally impossible as they said to reset the upgrade eligibility on my line simply because I'm an unhappy customer (who's been with Sprint for > 10 years)?