DTDC - Package Lost

Hi, I shipped a package to United States via DTDC on **rd march, **** after a month of constant back and forth with DTDC they told that the package was delivered but the receiver didn't actually received the package. The receiver provided all the proves to prove the package was not received to which DTDC acknowledged the package was lost. Around * months back they asked me to fill in the refund claim. Since last * months I have been fighting with them to get my refund. It has been a real struggle and frustration for me to get my refund. DTDC support team does not reply until I write something harsh to them. They do not care if they lost the package and the customer is suffering from the last * months