No communication from Woolworths

I went to festival mall Woolworths today and I can say I'm not happy with the service from management. I created a voucher to buy only to find that when I went to the till they told me I can't pay with it as they don't have an option for voucher payment and they were not aware. I then asked cause I can't pay with the voucher that I created I could have created another voucher . Mr Patrick Mokoeana the store manager stated that there's nothing they can do. The problem is I can't cancel the voucher