10% VOUCHER

Hi today went to clicks and I bought good for the amount of R151.90 . I told the teller that I have voucher however not sure if I have it in my purse and he billed me ,just before I went out of the shop I looked for my voucher and I got it . I asked the assistant at the shop to help and she told me that it is not possible then after few minute she agree to redeem my voucher however she didnt void or cancel the whole groceries that I have bought .She only took the Pantyliners and void using the voucher and she gave me 10% on the pantyliner only instead of the whole groceries bought . my question is why void 1 thing when I bought for r151.90 as I was due to get 10% off the full balance of the groceries . This is ***** and dishonest . I would like you to investigate the matter and come back to me . unhappy customer .