Why would the lady's whose kids I babysit fire me w/ out me knowing?

I didn't like this job anyway so I was online searching for babysitting jobs in my area. When I come across an ad she posted on sitterciry.com. In the ad she stated that I slept and didn't watch the kids! Wow, the only time I slept is when I got there (6:45am) all the kids were sleep, and she's the one that told me too! The thing that makes me mad is I never got a text, call, email or anything from her. She probably got this false information from her lying kids or even husband. I was planning on quitting this job because I'm getting taken advantage of. I babysit for like 12 hours a day 5 or 6 days a week and I get paid $75 a week for it. And one time it was suppose to be my day off but she needed me to babysit and her husband was there the whole time! What do you think I should do? I'm only 14. Oh! And she still owes me money. And I'm suppose to be babysitting tomorrow.