Final settlement and Experience certificate

Hello, I resigned in Dec 2017 from company (IT software) with one month of notice. I requested them for early release due to personal reasons, that they agree initially. Later company refused and asked to complete 30 days notice period. I requested them to settle short of notice period with salary and situation due to which I can not complete notice period. Company refused. On day of requested date of release my reporting manager did necessary formalities and gave me copy of signed non disclosure document. I left organization with short of notice period. Post that I didn't received any salary and Full and Final settlement. On contacting back, company said my case was of volunteer abandonment of job so final settlement and service letter will not be issued. I have all in writing (emails); 1. resignation 2. Last day working from HR 3. Early release request and offer for salary adjustment. Post that I contacted by emails and received no response. Kindly suggest what law says about such condition? Can short of notice period will be considered as abandonment? Company can hold salary and service letter both? I think it is simply harassment on companies part and it owes my salary. Please advice.