2005 Hyundai Elantra Advice

I went in for an oil change last week and said there is a svery slight squeal when I brake sometimes. They told me I needed all 4 rotors replaced b/c of rust. $500 later, my brakes still squeal and it seems that they squeal even more so than before. I took my car back and they said it was a rock that was causing the noise and cleaned it out. Driving off, the brakes are now squealing with every pump on the brakes.
What do I do at thispoint? Take it back again to get fixed? Ask for my money back(I couldn't afford it in the first place being a teacher, but they said is was necessary).
Thank you so much for your help :)