Why offer an voucher if you don't get it ?

Hi there,i'm a fisrt time shopper on Superbalist.com and where checking their prices and products on offer for a while before I decided to buy. On the date I decided to buy the offered me an discount aka "payday35" on which I added all to my cart and on checking out there were 4 times that the transaction"hanged"and then a message saying it was declined by my bank. At that stage there were more than R100k in my account and I went to my bank (Standard bank) to ask why it was declined. They assured me that the problem didn't lay with them and that surely it was on Duperbalist's side... I made an online purchase from another place just to test it and it went through like a hot knife through butter. I'm an accountant of profesion and it's tax season,so I'm busy. 6 days later I questioned them regarding the declined purchase and were assigned to a Lady called Holly She just bluntly told me that they make use of 3D banking and that why did it take me 6 days before I responded on the matter and that the voucher expired so I need to pay the full price. I don't have time just to sit around and query purchases, so when I do have time i take it up with them. I don't understand why they just can't eccept the fault in tge system and give me my voucher discount ? It's not like they loosing money as it wouldh've gone for the price should the system allowed it that day ? I send a reply to Holly but up to know a week later she didn't even bother just to response...Am my mere purchase of almost R 3000 just not important to Superbalist ?