Unauthorized bank charges

I was charged a R500 fee by FNB for which there is no explanation as my banking fees only amount to R300 and charged on the 16th of every month. I attempted to get an understanding from FNB for this amount countless number of times but with no luck. The "team of bankers" only ignore my messages or give me a generic response that hives no explanation of why my money was actually debited. For FNB to be taking money from clients in these trying times is poor taste for a bank that is claiming to be "helping" its customers. Are they forcing their customers to take debt relief and owe them by taking all the money in their accounts!? If this is how FNB plans to fund its debt relief fund by ******** customers that actually pay their debit orders then I will be taking my business else where as I will not continue supporting a bank that simply takes money from its customers for no reason