short changed gift voucher

I received a gift from a friend and unfortunately the top was laddered. The tag was still attached but no receipt. I took the top back for me to exchange it or get another top. The lady at the till scanned the tag which showed R89.99 however she gave me a gift voucher for R59.99. When I asked why she told me because the top is now marked down. This was a gift and I found it so unfair that I was ****** of R30. The lady that assisted also did not help the situation with her attitude. What sort of customer service is this?<br> Not happy and extremely disappointed. I am a regular at Mr Price and did not expect this.