Want a written apology for humiliation and embarrasment

I paid an amount of R15 152 towards my RCS account on 27 August 2019 as this was the settling amount which I discussed with another agent on 27 August. She said that the money will reflect by Friday 30 August or latest 2 September. I needed to use the card today at my local Pick n Pay store in Springs for a few groceries and upon swiping my RCS card, this card declined and I was very much humiliated and embarrased by leaving the shop without food for my family and baby. The woman I spoke to over the phone from Pick n Pay's customer service desk, carried on as if I cant count. Now all of a sudden, it takes 6 business days to reflect and not 5 as per the first agent I spoke to last week. WHY can RCS not allocate the funds when I pay on 27 August 2 days later? When I do my month end payments on the last day of the month, the funds reflects 2 day later. But if I pay the account on the 1st day of the month, I get an sms on the 3rd of the month from RCS to say I have paid a day late. WHY is that? I need a full explanation and a written apology from RCS for the embarrased and humiliating moment that I had to leave my trolley behind and walk out the shop. RCS can actually close that account for all I care as I will NEVER make use of their services again!