Arrangement not honoured

Am experiencing the worst service ever by FNB. Have sent them numerous emails and no answer. Made an arrangement with their legal company to make payments to my fnb Cc. FNB then decides to debit my account because there is money jn my account. They blatantly ignored the standing arrangement and refuse to refund my money less arrangement made. Why make an arrangement with YOUR affiliate and then just debit because I bank with you. I cannot feed my family because of this amount debited, I won't be able to get to work, IN ORDER to make the next payment. I am considering closing my account with fnb... considering this shocking treatment. I actually like banking with them. .. I have tweeted and emailed and posted on FB. The Manager Christopher said he would give feedback FIRST thing today.. and I am still waiting. What's the use of making an arrangement if they do as they please anyway.. they are all reading my emails but not responding or acknowledgement. I am highly frustrated and will make my way to Banking Towers and cause a scene. We all work hard for our money.