Gift voucher money missing

I was given a Gift voucher on the 8th of March 2020, then lock down happened. Yesterday i go to Mr Price Sport inAlberton City to get new gym clothing to be told the voucher has a nil balance. ( how strange as i never used it) i stand around until i say they need to phone head office as you can pick up with the voucher number where it was used and when. The teller does so eventually and the lady on the other side of the line promises to get us feed back. I have the ref number: 448514 name: sne in accounts

Now am embarrassed and pay with my credit card. This morning i go to exchange to leggings for bigger the teller ask me if i want feed back on my query.

This is unexceptable where did the R500.00 rand go. Am waiting for feed back and no answers. The voucher was purchased at the Mall of the South by my sister in law for my birthday