Horrible service received from Cindy at Jet Clearwater Mall

Horrible service received from Cindy at Jet Clearwater Mall. I got a voucher to redeem when spending R500. I went to the store to make a purchase. When I got to the tills there was only one cashier, I waited for my turn. Cindy rang my items and I informed her I had a voucher and showed her my phone, she asked me to call out the voucher number,with so much attitude. I called it out and then eventually she took my phone and tried to redeem the voucher, after trying it a few times she said it doesn't want to go through. When I asked her to ask someone to assist her she told me that the manager was on lunch and I had to wait for the manager to come back. She demonstrated a no care attitude and no willingness to assist me as a customer. She told me it's not her problem that the voucher doesn't go through and moved to the next till to assist the next customer on the queue. A colleague named Thabang came to assist me until he got the voucher number right.