Flies in Prawns

During December 2015, I purchased 4 x packets of Prawns. 3 of the packets were consumed during December and in January when I took out the last packet to be cooked I noticed that there was 2 flies in the sealed packed of prawns. I immediately called the store and spoke to a Macdonald who worked at the fish counter. He apologised and asked me if could please return it to the store and that they will refund me as well as compensate me as I had to drive from Hurlingham Manor to Fourways to return the goods. When I arrived at the store he told me that he would refund me and that he will call his manager so that I can have a word with him. I am not sure what was the manager's name. The manager arrived and told me that it was not their fault and that he will let the supplier know and I should leave my name and number and they will contact me if the supplier has any free stuff to give away. He then told me, that was the least that he could do for me as it was no fault of theirs. I just couldn't believe the audicity of the rude manager and I told me that I will do what I need to do and that I will not leave my details with them. He then very rudely asked me what do I expect him to do