Maggots from checkers

I went to buy some cat food at checkers in canal walk this afternoon the soft wet packets. I took 6 of them ,paid and left. When walking I smelled something wasn't right and checked the bag. The packet was open and there was maggots walking all over my bag with the rest of my goods. I turned around and took it back. I did not get an apology and on top of that they made me go fetch my own replacement as if I was not inconvenienced at all. This was so disgraceful of them. what type of service was that? And maggots? Really now...