Wrong gift card issued

I bought one voucher of R800 from sunglasshut sandton mall in Nov 2019 expiring on 27th nov 2022..i went there on 25th nov with voucher and gift card but they were saying this card is expired and there is nothing in tjis..there is another gift card number on voucher but they were saying its not uploaded in system..we said to them where is our mistake in this bcoz that lady who issued us that card may be she gave us wrong card or whatever..but they are saying we cNt help in this..if they cant whonis going to help