Refund process a nightmare even after the fault was with their system

I bought two items online, the order was confirmed and I went on to pay for the items, later on my order was confirmed. Three days later, I received an email, apologizing for the inconvenience cause as I was advised there was an error with their system and the items I purchased where in fact out of stock... Fair enough, they will provide a refund... How ever for me to get my refund back they are asking for a million documents (Which were never submitted with the purchase) due to the in availability of these documents it looks like they are not prepared to authorize my refund. This order was made on the 18th of December and until now I am still waiting for my refund. I am angry!!!