Hi China Post,
My item was marked as shipped on 18th of Nov. but I haven't received my item yet.
When I track my item (LX102699755CN), it landed in Melbourne, AUS on 8th of Dec. Since then it has had no any movement at all. So I called Australia post office today(24th of Dec) and they said they haven't received the article from the airline yet on their system and I need to talk with sender for the request of investigation for missing item to post office because it must be made by sender and lodgement claim compensation also must be made by sender.
So I asked the sender to request an investigation of missing item to australia post office and told him if it is lost by post office claim compensation to post office so i have to get a refund from you. But the sender dosen't want to do that and dosen't want to give me a refund as well. He just said track on ems china web site by yourself, if Australia post office hasn't recieved they are not responsible.
Can china post office help for investigation if I or sender asks?
No item delivered to me and no refund to me, so what should i do to protect myself?
I bought my item on ebay. So i opened a request on ebay but im wondering that ebay can refund to me because the sender shipped my item and he dosen't give me a refund and it's post office's fault.
Thank you in advance.

Australian customs are very strict, most likely it's in their hands. Your post office cannot interfere with customs inspection. Nonetheless, your seller is responsible if the shipment does not make it to you. Open a dispute with eBay or Paypal.