Pick 'n Pay Pinelands

am very disappointed from the service I have received at PnP Pinelands 23 march 2020 time 13:40 . my story is I have been given Voucher of R500 from my medical scheme so since there's lot of ****s I asked cashier Nomandla to test if its working and ask if I used it to test (PUMP WATER) amounted R10 wont that be a problem if now I want to spend the remaining amount SHE SAID NO that will not be a problem so I went inside the shop buying stuff when I am in the till I was told the voucher is not active I told them I just use this voucher 10 min ago buying Water .

so they told me I can no longer use it.. imagine using only R10 from R500 BCZ of a person who doesn't know their policies where's I did ask if we purchase the water wont that be a problem and told NO THAT WONT BE A PROBLEM I will be able to use it again as there's a balance of 490 .