Refund not recieved

I returned an item which i purchased in February 2024 online at Adidas. The item was collected 20/02/2024. Up until today i still have not received my refund/money back in my account. I have made numerous calls and provided them with my bank statement as proof that the funds was not refunded but still no funds paid back to me. On every occasion that i called the customer care line i get told that they as busy investigating and i must give them 4 days to resolve the issue. Its nearly 2 months and still nothing. I am very disappointed in the service i am currently receiving from Adidas as the funds due to me is not a small amount.