Unfortunately, the conditions at Walmart are pretty much typical for any company in the retail business in America. Lousy pay, inadequate training, awful and often unsafe working conditions, abusive treatment by management; and that doesn't even begin to touch on the crap you have to put up with from the customers. Walmart gets all of the attention because they're the biggest, but the fact is most other retail outlets treat their employees just as shabbily.
And if you don't like it, that's no sweat off their ass. By all means just stay home the next time you're scheduled to work; they'll just call the personnel office and have them start going through the stack of thousands of applications they have on file and start calling people in for interviews, and in the meantime your former co-workers will be expected to do your work as well as theirs until they get around to hiring someone else. There's never a shortage of fresh grist for the mill, especially with the economy the way it is these days.