Not releasing the f&f amount even after acceptance of resignation

Dear sir/madam. In September 2017 I joined a company who forcefully asked me to sign a bond and after one month time all of sudden company HR asked me to resign stating some statement and asked me to resign immediately otherwise they will terminate me as per the clause mentioned in bond , where it was mentioned that employer can terminate the employee anytime without any reason and can release him within 7 days or immediately by paying him 7 days wages .... So forcefully I resigned and they release me on same day with acceptance of resignation on company letter head clearly stating that I resigned on this date and is immediately relieved and I should complete at formalities of F&F and that will be released soon ... After the resignation I tried to contact them but they are not answering my calls or mails and they have still not released my F&F amount ( one month salary ) . I have got the resignation acceptance as well as signed F&F sheet with me . Pls suggest what should i do .?