I work in a kind of similar environment (disorganization, not knowing things until last minute, heck we're even "spied on"!!). I put up with it only because I KNOW this is my last few months working there, and I KNOW I have something much better coming to me this next spring.

My suggestion, if you're only making minimum wage, screw that job, schedule a few interviews, because seriously isn't it some sort of law to allow you X amount of hours or days notification in advance of a work schedule? If you aren't technically scheduled, then you have no obligation to come in?

Even if you just got a job at the local pet store, or some store nearby, I'm sure that would allow you some stability while still making around the same amount of money, without all the BS you're dealing with now, to look around for another job. Because, trust me, I DO know how you feel, every job I've had in the past you are describing almost to the T!! But I'm sure you can find some filler job that pays about the same and definitely has better hours at some store within walking distance. And you know what? Go ahead and schedule those interviews!! You should NOT have to wait around by the phone if you aren't on-call for days where you don't even know when you're working or even IF you're working!! That is so wrong of them to expect!