Share certificate lost from karvycomputershare

Issue: We have sent a physical share certificate of Kotak Mahindra Bank for split to Karvy head-office but never received the split shares back. As per karvy they have sent it to us using registered AD however we never received it, on following up with post office, they are saying they lost the post sent from karvy. and karvy acknowledged it. We as a customer don't know what karvy sent us and what was the post post-office lost. assuming it was certificates, it is karvy's responsibility to issues us duplicate shares, but they are denying it. After lot of back and forth they are not understanding the fact it is not lost from us, infact it is lost from them technically, they are asking us to complete the lost share certificate procedure to get the duplicate, and no cooperation from there side They are requesting FIR and Surety along with many things from us to issue the duplicate certificates. Police is not ready file and FIR as it was never lost from us infact it is lost from Karvy and/or post office and hence it is there responsibility to log an FIR. and on the matter of surety, the market value of share's are high enough that we cannot provide any surety from any of our friends, we asked them if we can provide surety based on purchase price of the share. but they are not cooperating in that matter too Its been one year(from March2017 until today) we are unable to get the duplicate certificates. what should we do. we even requested them to issue us in demat account if not physical certificate