The staff at Game Trade Route Mall - Bad Attitude

My mum opened up an account at Game so we went to collect her card and upon receipt of the card she was given a voucher which she could use for any purchase of R4000 or more. My mum had forgotten about the voucher and only remembered after the transaction had gone thru, so we then told the Cashier about it and her response was that she could not help us as it was too late. I cannot understand this as we where still in the store and it was merely 5mins after the transaction had gone thru, furthermore they were so rude to us, My mum is a pensioner so I handle all of her accounts, when I had called into lay a complaint I was transfered for our 10 mins to three different people except for management. It has been almost two weeks and still no one has contacted us. I wish we had never opened up this account. The best part is that the Cashier told me to keep the voucher and use it at another time and the Voucher has an expiry date on it. In my opinion I just think that the cashier treated my mum unfairly because she is a pensioner.