Sent Fragile Car parts damage during transet

I have sent some car parts down to Durban (Westville) from Pretoria(Bluvalley) I told them to mark the parcel as fragile and make special instruction that the item was very fragile as it is carbon fiber for a BMW M4 I made sure that I had bubble wrapped it numerous of times to make sure it was secure if dropped I also gave them a special instruction to make sure that the item was not to be double stacked on only to find out when the parcel arrived at my customers place he found it to be damaged like it was double stacked on and it cracked the carbon fiber the parcel was sent via courier it via Postnet now no one wants to accept responsibility for the damages and leaving me liable for the damages which is unfair as we pay alot of money to send the stuff down and I am a loyal customer of Postnet very upset with this as the item is worth R3000 leaving me responsible. Very unfair and *********. I think either Courier it or Postnet should be liable for this as I done my fair share. Very disappointed customer.