Adidas don't pay refunds

I order a product they say is in stock. I buy 2 items online. I get only 1 with a mail stating they are out of stock on the 1. I paid for 2 items & when I checked out it was paid for 2 items. When I ask about the refund back to me for item not delivered, they say only 1 item was captured & only 1 item money was taken. I send proof they request & up till now (2 months later) they still investigating & no refund. Beware of this when you buy from Adidas