Can I get duplicate share certificates if I lost the original copies

there are shares under line in my parents name in physical form that is they are not dematerialised. some of the shares have been returned to the company because no one was there to collect them and some of them have been misplaced or lost. the total value is very high. from the phone calls I am making to the company RTA that is register transfer agent I seem to be under the impression that he is unnecessary prolonging and avoiding to issue duplicate share certificate or help me expedite the process. one thing for sure we have found out that when the share certificates for return back to the company and when we have been asking for share certificate they have not sent it to US and then they write a letter to us asking us to dematerialize the shares at the earliest. I want to know legally what is my right as a shareholder of a company I have the right to have duplicate share certificate after I declare them as lost. I also have the right to claim share certificates that have been return