Ecom Express — complaint about my product which is not delivered to me and in status shown delivered

My packet is mean to deliver on 9 september and i wait whole day for delivery boy but at the end of the day i check status of my packet its shown delivered even there delivery marked my signature and on the other side i didn't even get my packet and after that i complaint about it on customer care at that time they answered it take 72 hours to resolve your problem and after that i call complaint center so many time but i always get this response like it take 48 hours to solve problem it take 24 hour it take 48 hour always they give me time and i wait and even after 15 days i didn't even get any solution even they just listen my first line about my packet and after that they just answered its takes 24 hour or it take 48 hours and all i really wants to know in which world my packet gone what happen to that they even promised me your problem is solving on priority base but i still didn't get any results help me my packet id is [protected] and my name is keshav