RCS Declined Purchase - Then debited the card twice for the same purchase!

On the 24 August I made a purchase at Builders with builders RCS credit card and RCS was offline - builders was not aware. The purchase was put through twice at the till - both times it was declined. I then made the purchase with another credit card. I wanted to make a purchase and then noticed my available balance was too low and that the purchase had been put through to my RCS credit card twice. I phoned on the 26th and was told to wait 48 hours and the double debit would be reversed. It did not happen, I then phone again and was told to go into Builders to fix the problem. I did - Builders has been trying on my behalf to get the amounts reversed but they are getting no reply. I was told to wait for 7 days and again, no reversal - just phoned RCS and they tell me now I must wait 14 days. They are unable to reverse the amounts which is not a small amount.... so in total, I have now paid x3 for one purchase. Is this to get interest for the month on the amount? I cannot be held responsible for the above amount or the interest and very willing to go the length on this. I have never had this problem with builders, when I return an item, why is it that RCS, is not able to do the reversal? This is not 1920 and the ledger is written in pen. It is a simple accounting reversal, one puts through your accounting system. Correct? So when is this going to be fixed or do Builders and I take further action?