Lose my parcel and call me the *********

Internet Express have admittedly lost a R420 parcel of mine (with no apology) and will only refund the cost price, not the retail price. The actual cost of this lost parcel is the retail price of R420 though as they've lost this revenue for my store whether the customer opts for a refund or replacement I am still R420 worth of revenue down due to their loss of my parcel. They're also claiming I'm committing ***** by claiming the retail price, they lost R420 worth of products and will only refund me the cost price and I'm the *********? P.S. This is a limited edition product, only 16 in stock and all proceeds from its sale are donated to an animal charity.