Sell products way after the sell by date

Pick n Pay Hyper in Bloemfontein doesn't inspect the pet products regularly for the expiration date. I bought the AVI parrot food from them and didn't realize it had expired. Only after my parrots got sick and died I realized it. I informed the manager a Mr Ishmael about it and when we went to the shelve all the packets were expired by almost 3 months. He then offered to replace the parrots out of his own. Jeanette also from the shop called me to get the proof of purchase of the parrots and when they realized it was expensive the cat and mouse game started. Almost two months later I was told by the insurance company that because I didn't took the parrots for a autopsy and to a VET to obtain a report they will not replace them. They offered to replace it and not the other way around.