Non payment of matured bond

Location/place: Kolkata

Name of company/service: Sumangal Industries LTD,Kolkata

Purchased 5 Potato Flexi Bond amounting 320000 in total from Sumangal Industries Ltd ,(Chatterjee internation centre,9th floor,room no-A-11 & 20th floor room no A-11 & A-12,33-A,J.L.Nehru road, Kolkata-700071),around April 2012. Bonds matured around 28th July and 7th August 2013.Already deposited bond papers for encashment of bonds. Pursuing for last 6wks for the maturity amount but with no results. Post-phoning every week. Please help,so that i can get back my money.