I think the problem is that even though you had told them what you expect and what your hours are, they have been used to you bending the rules and your expectations for them. So they think that it won't matter...you'll just go along with what they change things to. Now that you've put your foot down, they are having a fit because they aren't getting their way. Which unfortunately happens way too often in this business.

I would suggest seriously thinking about what you are willing to be flexible on and what you're not willing to do anymore. Then let them know and if they don't like it, you can remind them what your original agreement was.