Pick n Pay horrific service to lower income group

I received a voucher from another potato chip manufacturer because of something I found in a packet of chips. I went to Pick n Pay in Cleary Park in Port Elizabeth and was told that they do not accept vouchers. I was floored... I have in the past used vouchers at Pick n Pay with no hassles. The supervisor at the till was not very forthcoming when I asked why. I then asked to speak to a manager and the manager never came. I was told to wait whilst she goes to fetch a manager. I saw this supervisor going up and down doing her own thing, but the manager never came. I called The PnP Customer care line and I was also not assisted and they lady said she would call me again on Monday as their Head Office was closed on Saturdays. My gripe is that the overall service in Pick n Pay in Cleary Park is always atrocious. The staff is not helpful at all and the queues is usually terrible. You rarely get the promotional items advertised, so I usually go to another Pick n Pay that is 30 minutes away from where I stay. This is also not right as why should we be content with the bad service when the stores in more up market areas has good service. Does Pick n Pay not have a standard across all their stores. Are we supposed to be content with bad service because we live in an area where there are more lower Income people? Is our money not the same as any other money I am still to get feedback as to why my voucher could not be accepted. I bet that if I were in a different store my complaint would have been resolved by now.