Don't mention why you left, just mention it for the experience you now have.
If they ask why you left, say that you quit because they were asking you to work more hours than originally agreed upon and they refused to reduce your hours when you asked.
Hiring managers will understand that a 17-year-old working a part-time job has to have limits, and its reasonable that you would quit if they insist on scheduling you for too many hours.
Also, it's not lying to say you quit. You made the choice not to work the hours they demanded from you, and both sides agreed that would be the end of your employment. Since it was your decision not to work when asked, you sort of did quit, even if you didn't give notice.