If you can't work the hours they need you to then maybe it's not the job for you.
I am contracted to certain hours in jobs I've done with an additional contract stating that I work additional hours as and when required. I often work many hours a day passed my contracted hours as that is just how it is. I've had jobs where I've been in up to 3 hours early on a daily basis and stayed upto 5/6 hours later on a regular basis and then come in on weekends.
My lunchbreaks can be meetings or just worked through, I can be out on a work do all evening but still work at leasr my contracted hours without any additional pay or similar.
I have a job, that is the important thing for me, especially in the current economic climate. Many people have had to work longer and harder for the same or even less money in some circumstances.
Unreasonable treatment shouldn't be tolerated but asking you to work your contracted hours is hardly unreasonable.
If you can't sort the issue to your satisfaction, maybe you should look elsewhere for a job if you feel that badly treated, somewhere you can work set hours with a set lunchbreak etc...