Lost package/ no reimbur*****t

My international package was received by the durmail branch on 8th November 2018 tracked online. Suspecting the system didn't update I contact the call centre to get my local tracking number in December and only receive a reply in mid January with my tracking number. I made a few more calls to fetch it myself from the durmail branch as it hasn't moved since November only to find out that the package was not at their branch and hasn't been checked in to any other branches. The package was lost in transit and I was told to get a form filled by the sender for a enquiry but the sender is from china. The SAPO has been nothing but *********** in dealing with a lost package. It's a fairly large package and quite expensive too. Until now I have not received any information about the package from customer services and no way to be reimbursed for the lost package by the post office.