Company not paying my dues even , I have all the document like releiving, hand over certificates,

I have simply resigned from company due to more work burdon and facing stress , instead of 45 days of notice I have only give 18 days notice . First my HOD is not want to receive on 18 days . But finaly they receive on same date. And I have get all document like hand over , no dues of all department, relieving letter from HR. Now it's 2 month of continues mails, phone, whatsup to HR for settlement . They are giving confusing reply like payment is under process on phone and whatsup only. Not replying in mail .And now HR says that my department HOD says that I have not completed my pending work. Some how it's posibility of some work pending so that no mean they can forcely back me in office for pending work. And also no proper working system in company . HOD is blaming on junior if any fault . I was also a executive level employee not the manager level. Now my 18 days salary, gratuity , earned leave is pending with them. Pls suggest how can I get my payment and can the company take legal on pending work but no proper job profile distribution their .