Fixed deposit in cooperative banks

Dear all, I have questions regarding withdrawal of fixed deposit from cooperative bank. Actually my grand mother(maternal) had fixed amount of 75000 RS, 4-5 years before and kept my mother (youngest daughter out of grand mother's 7 children). 3 years before she expired. We approached bank to get the fixed deposit to my mothers account but bank refused to do so and they need original fixed deposit certificate which we do not have and hope it is with my uncle (younger brother of my mother). We don't have good relation with my uncles family, so they said they don't have any such certificates. Now we are confused and not know the legal way to get the amount fixed at bank whose nominee is my mother. Please any one can guide me and my family to get our rights. This is all about "justice and rights".