Adidas - No refund for returned product

I ordered a pair of shoes from adidas that qualify under the return policy. The size was small and bigger one was out of stock. Hence had to return the item. It was picked up the next day after delivery with all tags intact. They shared a payu link for refund which I filled on ** April before it's expiry. But not refund has been processed yet. I have been calling them they're not answering. On email, they mentioned the link expired on * May because I didn't fill whereas I did and I have the screenshot to support the same. They asked me to wait at max * days for new link but it's been more than a week now. They're now not even replying not sending any link or money. Please help me get the refund. It's a lot of money for me