Pierre Cardin Sent Wrong Dress Size with No Exchange Options and Delayed Refund

I ordered a Pierre Cardin dress online in size 36, but they sent me a size 40 instead. I can't find the item anywhere in Istanbul, and customer service advised me to return it online for a refund since they said exchanges aren't an option. They recommended checking out a store, but none of them have it available. They said it would take 15 days to process the refund if I sent it back. They can only buy it again, but size 36 isn't available anymore. I'm really disappointed; I needed this dress, and this is just not okay. This is definitely going to be my final buy here.