Dissatisfied with Employees & Algorithm of Steve Madden App

I have a very bad experience with Steve Madden on their website/App transactions.

On the 26th July I made a purchase while they had an extra 25% off on sale prices, unfortunately it seems like there was a system error and the transaction did not pay items on the cart. 2days after I checked only to realise those items were still on my cart but unfortunately the amount of R742,50 was deducted from my credit card. I have been in contact with them and unfortunately no one seems to know what to do. I do not know do they not have IT or Finance department within their company that no one seems to know where to start. They know perfectly that they App algorithm is not user friendly yet their employees who answe on this queries does not seem to have used the App ever in their life yet they have the audacity to refer me back to the unuseful App.