Selfast Fashion Stores Unclaimed

I made a purchase at selfast chatsworth on 26/01/2017 and paid electronically , after the payment was made there was a power failure , the store clerks where adamant that the payment did not go through because they did not receive a printout , I returned later with proof of payment but they where still adamant that no payment went through , in the interim I paid cash for the goods purchased and was asked to return a day later for a refund , my wife called on the 27/01/2016 and spoke to a clerk about the refund and was told that she will phone her bank and verify payment , waiting for a call back from the store clerk , so basically I paid twice for the same goods at the store and they don't seem to see that this is not how businesses should run , I spoke to the manager at the store as well but he did not understand how electronic payments operate , I emailed a complain to their website and I was not contacted nor did anyone call me to resolve this issue ,