Employer cheating to pay my salary

Hi I am working as App developer and also while saturday and sunday I work as trainer. 2 months back I joined in a Training institute called CITS which is situtated in chennai. They told me while hiring me that previous trainer was left due to his personal problem, So you need to handle the class from the beginning and once the batch completed then we will pay you the salary. But later I came to know that the previous trainer also left due to not paid. I know this from one of the student For that I spent more time, fuel to reach the institute and finally I completed the course to students. Then I start asking for salary. The person who discussed with mewas left from the job so contact other person who is handling his jobs, later he avoids my calls then he ask me to contact the one of the owner then he also not picked my calls then finally I contacted the person who discussed my salary and number of students etc. That guys asked me to contact previous guy. Currently one month was completed but I am not paid. I lost my previous job also because of this training institute. I can't tolerate that I was cheated and now a days I lost sleep in night times and keep on thinking about this problem. Planning to file a complaint and sending notice but both will make me spend more from my side. Please advice me how to handle this.