Company not settling Full & Final of accounts

I have worked at a level of Assistant General Manager with one pvt. ltd. company for six months. While leaving the HR department has taken a stand that Full & Final settlement will be done only after collecting NOC from the business associates appointed by me. In my appointment letter there is no where mentioned about this. Is senior person like me has to collect NOC because I was not at all involved in direct dealing with the business associates. It is only applicable to the front line people to do so. Now the HR people have stopped answering my calls also. Now steps do I take to get my salary plus traveling expenses I have incurred before leaving the company. My resignation was accepted within 5 minutes on mail by Boss Director of the company. Kindly guide me as it is already a month I have resigned . There are so many other employee also who have left but the company is not settling their dues.