Sharekhan — Lost share certificate

We got sharekhan account opened for my parents and gave aadhar card and other required details for address and even informed them the current address is the permanent address.
My parents had hard copy of share certificates which had to be converted to soft copy and added to the account created.
1 of the share certificate had some issue and had to be returned back to my parents but sharekhan sent it to some random address and not to the address provided by us. When checking with them they are telling that we have sent to the address as per election card which we submitted as we were asked for and not as an address proof. Now the share certificate is lost and sharekhan is not taking any responsibility for the same.