Poor scheduling, few hours - English Tutor C2 Education Employee Review

When I was hired I was told I would be working 32-40 hours per week. But even after 2 months of working at a center, my hours would fluctuate between 4-12 hours per week. The center director keeps promising me more hours, but each week I receive barely any. The center director has given me no indication that this is a result of my performance and she seems eager to "keep me on the team." It's absurd that they expect me to set aside 7 days per week and then only call me in for 1 or 2 days. This means I can't, say, make plans for the weekend because they won't let me know more than 2 days in advance if I have that time off or not. If I tell them I can't work on a certain day less than a week in advance, the CD gets irritated. But am I not entitled to the same irritation when they tell me 1 day in advance that I will/won't be needing to work. (This is why I gave work/life balance 1 star; they own all your time, 3pm-10pm, whether you end up working or not.)