lost of parcel

On the 9may 2015 I posted a parcel to the value of R1600. Using a postoffice speedy courier with johannesburg cbd jeppe street post office, my parcel was suppose to arrive the following day, it didn't arrive I went to the postoffice 2 days after I was told to come back the next day I went back I was not assisted, I went back on the 6may I spoke with the supervisor she told me my parcel has been opened and ******, she then gave me a claim form to fill out and fax it to a speedy service supervisor her name is zodwa on the number ***,zodwa rep**** a week later saying the still investigating, I've never her from her again till on this day. I had to refund the my client her money which was R1600 so I have lost that money to postoffice I am extremely disappointed with postoffice and I am not happy at all. And I was told that they will not refund my money and I don't know what to do, I wish I could get answers to what happened to my parcel I feel like I've taken my money and flashed it down the drain this is so frastrating and sad