I have found that going to actual stores and even kiosks is usually better than dealing with the phone reps. Some stores earn on commission, so they would want to keep you and get the sale, some stores (the one I deal with) aren't on commission, so they dont give a damn about getting business through sales. Instead they dont give any BS, and get/keep customers that way.
Try going to different sprint stores in the area, see if you find one with a good sales rep/manager to explain your situation to. Might find one that says the crashes are enough to warrent repair/replacement and do it for ya. I had an old phone which wasnt broken, but battery life sucked all of a sudden, sometimes lasted 0-2 hours, sometimes a full day (after full charge, so I guess you could say it was broken in a way) and instead of charging me the 50$ replacement cost that insurance would have, they replaced it for free of charge.
The other option is if you have full insurance w/ replacement plan, manage to "lose" it. I am not saying to be dishonest or anything, but at this rate I am wishing I "lost" my mogul a month or 2 ago.
Honestly though, if its having the crashing issues that is making it dificult to use (esp as a work phone) then technically it's broken. If its broken they should replace it. If they wont honor their end of the deal (replacing broken stuff) then I cant be held accountable if by some chance my phone falls from my pocket and ends up on the garage floor while I am working under my car and I dont realize until I have already driven over it. Havent dont it yet, but thats just my $0.02.