Madame Coco Refunded Me For Only 3 of 4 Returned Items and Won’t Resolve the Issue

I recently bought a few things from Madame Coco’s online store, but when the delivery came, I saw that the courier was pretty rough with the packages, even tossing them onto the ground. I turned down the delivery and quickly sent the items back with the courier. I got in touch with Madame Coco to let them know what happened, and they told me that only 3 of the 4 items I sent back were processed for a refund. I've followed up several times and explained the problem again, but I keep hearing that it's still being looked at, and I still haven't received my full refund. This has become a really exhausting experience. I just want the refund for the missing item to be handled like it should have been from the start.