Fish has given you some great information in his informative post - pretty much covered all the bases. All that I'd like to add is not to accept even the slightest bit of dishonesty or lack of integrity on the part of your employers.

There was a time when honor and rightousness were mainstays in China - dynasties rose and fell because of it or because of the lack of it. These days though it seems as though a huge percentage of the population is not acquainted with such ideals. Or if they are, it just doesn't fit in with their personal agendas.

The reason, though, that I say "feel free to flee" is that there is that portion of the population that is honorable and rightous. If it's necessary to "do a runner" so that you can find someone in that population to work for, well, so be it.

You will be no less a man, nor will your own integrity be damaged if you seek employment elsewhere if you recognize that you're not being treated honorably. In fact, you will not be acting vengeful by leaving. Quite the opposite - you will be making your employers consider their actions in light of the reality of your choice.

My own code as a teacher in China for the last nearly four years is pretty simple. One lie is enough. One bit of trickery is enough. One broken promise is one too many. No second chances. Contract? F*** that - it's not worth the paper it's written on.

Bottom line - feel free to flee.