Bad customer experience

I'm extremely unhappy with customer service at local pick n pay in langa. I cannot go there to buy some groceries only to be sent back and I was told to come back the next day because the system they use is still new they dont have access to redeem vouchers, I was told to call them the next day which I did then they said they will call me back till now, no one called me. I wasted my time twice and no one can bring back my time, for me time is money. I'm stucked with their voucher.