Charged twice for one purchase

On the 23rd of February 2016 at around 12:30 I made a purchase of R199.97 at Mr Price in Randburg, I swiped my credit card and the cashier said it declined, I swiped my cheque card and the payment went through only to later find out that the payment had also been made from my credit card. When I enquired they assured me that the payment will reverse but to this day it has not reversed and now they are asking for my bank statements as if I actually owe them. Firstly they didn't even mention system problems. In black and white Mr Price Randburg has cheats and *****.