Online store useless

Poor customer service from online store. I ordered an item on 22 July 2022. I’ve hade several enquiries on delayed delivery as I had to wait for over 4 weeks, I then received the package on 15 August, but for some reason the delivery on the adidas system was captured as 26 July, now I need a refund and I’m told that the refund period has expired. I’ve provided courier proof of delivery as 15 August but they still refuse. I’ve sent them the courier tracking number showing when the package was delivered, but they still refuse. I’m so annoyed and frustrated. The online store is a ****!!!