Almost every teacher for every language institute has this problem.
The real answer is, there is little you can do without loosing your job, except be persistent and patient. It is why I quit the institute I was working for when I was an English teacher and started only taking private classes.
If you are here legally working, you can file a complaint with the ministry of labor and they will respond, but you will be terminated and possibly blackballed from other institutes.
If you are here working off the record, you have no rights, as you are illegal.
Here is a link to an ad for teachers at a small but reputable institute that I know will treat you better, should you qualify. Sorry and good luck.http://www.livinginperu.com/classifieds ... fications/