Double charge by FNB for a transaction

To say that am disappointed by FNBs lack of action to my previous issue would be an understatement. I wrote a complaint for the same issue on the 28th of Dec. Following that, hours later, some guy call from their call centre called me to tick the boxes regarding my complaint of a double charge of R1946.41 for a purchase made at Food*****s on the 23rd of Dec. This guy was not interested at all and just merely read some questions which obviously sounded very scripted to me. A team leader from the call centre named Goldie Lepu called me to advise that my query was being treated with urgency and the funds would be reversed within 5 days. Today is the 8th day and no one from FNB has given me any tangible feedback. In the meantime FNB charged me R110 for a returned debit which is as a result of them keeping my money and making no efforts to reverse it. Looking into my account it definitely cannot be rocket science to see that I couldn't have made the same purchase at Food*****s just seconds apart. Why is FNB keeping my money and purposefully inconveniencing me. What would be a requirement for me to close my account as am sure I can get a better service through another bank.