Adidas - Refund problems

I ordered and paid for a pair of shoes on 3 December. Adidas send me a mail telling me they are cancelling the order as they don't have stock of the item and I will be refunded. I have phoned and send emails for my refund. They say its being escalated to the "back office" and I must send copies of my bank statement as proof that I was not refunded. I told them to send me proof of payment and that I am not sharing my bank statements. I phoned on numerous occasions and send emails to the email address supp**** by the person that told me about the "back office" To date I have not had any reply from them and now I cant get through on their phone number either.