Humiliation with regard to payment of account

I usually am a good payer and pay more than I should at Edgars or anywhere else for that matter. I recently did a purchase at Edgars to be precise this was 3 June and I also did a payment of my account on the same date. Balance of my account was R210 before the purchase and after the payment. Purchase was R499 According to me all is well and I will pay my account at the end of the month. To my surprise I receive a text message informing me that I need to pay my overdue account. I ignored this but then I received another message informing me that I need to sort out my overdue account. I decided to go in to Edgars personally to sort out the problem. I went to Customer Care where I was told I have to pay approximately R305 Bear in mind, I had a balance of R210 and a purchase of R499 = R709 The most I should have to pay is R210 because the R499 fall in June the new month. Nobody can explain to me what to do, I was at Edgars for three hours on Saturday and about 10 people tried to assist. First or all they had me stand in the middle of other customers trying to sort out their mistake which does not sound very good to anybody listening. They put me on the phone to the head office and then they assist another customer where I am standing and moving out of the way as far as I could they start helping somebody else right where I am standing. You feel so embarrassed and humiliated, there is no sensitivity for the feelings of you as the customer. (It is like standing naked in public) Eventually I just left because the person at the head office could not assist, several other people could not assist eventually I was told somebody will phone me today, Monday 18 June to sort out the problem, I am still waiting. Somebody did phone me on Sunday during church to let me know they will do something about the matter and promised that I will receive and phone call to tell me what happened. I am still waiting. I cannot pay my account because that will not solve the issue. How do you explain this? More than three hours of my time and about 10 Edgars employees later for such a small matter and no solution. What is happening, are we as the customer left to the mercy of the supplier. In the past we could complain at Consumer Goods but this also does not even help these days.