How to get final settlement from ex employer

I was working in a company (a major auto dealer in the North Karnataka region) as AGM Finance & Accounts since Jan 2015. In March 2017 the company asked me to put the papers as they needed to reduce the cost. They said April 25th will be my last working day. However, they later asked me to extend up to 12th May for completing some works and handing over to new joiners. I agreed for the same and did as many tasks as I could till 12th May and did knowledge transfer to the new joiners. In spite of this, the company is not making the final settlement. They have not paid my salary for the whole of April and up to May 12th. I had stopped going to the company since 13th May. However, they asked me to come and clarify some accounting matters to the new joiners. Accordingly, I went to the office on 1st June & on 15th and clarified the matters.