Once off voucher at pick n pay , leaving our monies

Their redeem once voucher is ridiculous, so basically if you have a voucher for R500 ans utilize R110 you forfeit it and to think some cashiers will not even educate with regards to that , I mean when I pay the till I'm expecting the cashier to atleast ask me what voucher am I going to use and how much is it , am I aware it is redeemable once , basically 390 let with pick n pay where are these monies going to , even those R5 that are left from client vouchers are collected by Pick n pay simply because it's redeemable once .for me that is day light ******* to us clients and for a big company like pick n pay to be collecting remaining funds from once off redeemable vouchers is disappointing ..they need to review their system process with regards to this or train their cashiers to communicate before a purchase has been done ..imagine if is an old person and using a voucher that was gift and not informed of this prior ..I'm just disappointed in their process and hopefully they will take this review seriously and make adjustments