Not receiving payment from the employer, wanted to take action

I was working in a company and I joined that as one of my friend told that his friend have opened a company and as he is not having employees right now, you may join he will provide you 15K salary. He asked us to sign a paper on which it was written that if we are leaving the job we have to give a notice of a month or deposit one month's salary but he also told that as you are my friend's friend this is just a formality. We were meant to work for only a month. Before the month was over the owner who was my friend's friend started giving the hint that the business is not doing good so he may deduct some money from the salary but he never told us anything clearly. We left job on 4th he told he will pay us before 15th. On 15th he said that he will deposit salary next month and only 8000/- . What action can be taken so that we can get the salary and he learns a lesson.