Customer Service is an oxymoron. We can't really expect someone getting paid $2 over minimum wage, taking crap all day long, to be the most happy and helpful person. This goes with any company. I'm pretty sure the only time you get anywhere is if you catch someone who just started their shift. Apparently they're still lying to themselves saying it's going to be a good day at work.
On a side note, I've always found they work better with you if you are firm, but not angry and explain you know it's not their fault, but you need the problem fixed immediately.