Clients to assist themselves

I went to Game Bellairs for the first time and will be my last, the stores are very busy and patience is a must this time of the year, when i went to the till to pay for my items i had a trainee assisting and i had to explain to her how i was doing my transaction as i had a voucher which was a gift. I understand she is learning so not a problem. My transaction came to R 693 and i had R 300 on the voucher, she tried to swipe for the R 300 on the voucher a few times but it was not working she called a supervisor who tried and it also didn't work not sure why,The supervisor then told me that i must pay i asked her how do i sort out the voucher issue and she told me i must call the people that make the card my self and get it sorted out and started walking away, i was not happy with that response as the card was bought at Game and not from someone who makes the cards.i called her back and started explaining this and she walked away mid sentence. i went to the managers counter to complain, they then tried to assist and said the supervisor who assisted should of tried calling the people to assist in sorting it out, they could not get through so i took the number down, I will not be back