How do I get my documents and my Full and Final settlement?

Hi, I was employed with a small company since Jan 2017. I was supposed to take a leave on the 5th of March till the 11th, for which I had applied well in advance. It was to take my mother to Indore for her yearly eye check-up. My employer declined my leaves asking me to reschedule as one of the staff members was unavailable till the 10th. I was asked to schedule it after the 18th as others were also due for leaves after the 10th, though I had applied far ahead in advance. My mother was supposed to leave on the 14th so I left for Indore anyway on the 9th. When I came back on the 14th and contacted them, they asked me to not to come to office and instead send them my resignation. I did as instructed and received no response for 21 days. My follow up calls were ignored. When I finally got through to them, they said they'll email me back. They emailed back stating that "As per the terms of your employment, you owe the company a sum of Rs. 49,032. You must make the payment of the above amount immediately by cheque favouring XYZ. Please send the cheque to us no later than 21st April 2017. As per my offer letter, I am not liable to pay any such amount. Moreover, the company is in possession of my 12th Passing certificate and result, which they are refusing to return unless the amount is paid. Also, my payment for the number of days worked has been declined. This kind of behavior has been meted out to numerous other employees in the past as well. I would like to take legal recourse to get this sorted once and for all. Any help in this regard would be greatly appreciated.