Unfortunately, that's pretty much the way that retail is. I work at Wal Mart and I have seen the exact same thing happen there. They always find a way to work around your schedule and if you actually do it then they think, "Oh, well she CAN work those hours after all." The key is to not budge for anything.
Retail hates families. All they care about is business. You aren't going to find a place that is any better-not Wal Mart, not Target, not anywhere. Just keep fighting them about the schedule, look up policies about scheduling around availability, and stick to your guns! It's the only way you can make it in retail. Also, never quit. If you quit then you can't get unemployment which you may need when looking for another job.