Bank authorities not releasing house registry

My father died in January 2005. He was working in State Bank of Indore, which is now State Bank of India. He took housing loan which was cleared after his death. We were getting the registry of the house without any problems but due to security reasons we decided to keep the registry in the bank. Now after the merger, State Bank of India's manager are not even giving us a certified copy of the registry. Instead they give us a deceased claim form which is impossible to fulfill. It's been 8 year's and still not giving anything in writing. What should we do as my mother is retired and my earning is not enough. We want to sell that property..so that some financial assistance can be made.. please help