Frustrating. - Host/Server Applebee's Employee Review

I did well as a host and was told that in 2 months at my first job I would be moved up to serving full time. It took 3 months for them to fit in 5 training shifts, all the while hiring and training 7 new servers. I now host 5 days a week in the mornings, where I make no money at all, and I'm supposed to serve once a week. They've told me I have to bring in someone who will be able to host in the mornings before I can start serving more. I don't understand how it's my fault that no morning hosts are being hired. I'm constantly doing extra work and not being thanked for it. There's nothing I'd rather do than quit right now.