Sun1 over payment, Refund

I made a reservation on Bookings.Com during the reservation I made a payment R610.00 using my FNB check card, on the checking they made me pay again an amount of R542.17 and I paid using my credit card. This came to my attention when I received my statements and made a call to them requesting a refund, they check and made follow ups and they told me to fill some form and send my id copy and write a letter stating why i need a refund. This is my money and you made me pay twice for one booking of one night. Is it hard for you to reverse the money back to my account, I am not saying go and deposit money into my account i am saying reverse the payment , we didn't write letters when i made the payment so why the process when you have to return the money.