Product: Bank account or service

I am filing a complaint against Citibank regarding my Savings XXXX account ( ending in XXXX ). 
I check my online banking balances every day, and on XXXX XXXX, 2016 I noticed that the balance on my Citibank XXXX Plus account was {$490.00} which was {$4.00} short of the {$500.00} balance on my account the day before. I found this odd since according to Citibank online banking, there were no transactions posted or pending that took place to account for this {$4.00} difference. I sent a secure message to Citibank through online banking, and on XXXX XXXX, 2016 I received a reply back from a Citibank support representative " XXXX XXXX '' ( Reference : XXXX ) which said the following : " I would like to inform that Statement Savings Account ending in XXXX is enrolled in Basic Banking Account ( BBA ) package as standalone account which requires maintaining the average monthly balance of {$500.00} or more to avoid the monthly service fee of {$4.00}. The average monthly balance is calculated on balance of account and the monthly average is adding the daily balance of account for 30 days statement period and the total amount is divided by 30 ( days ) ; not ending balance on the account. Since you have n't maintained the monthly average balance of {$500.00} for the XXXX/XXXX/2016 to XXXX/XXXX/2016 statements cycle, your average balance was {$400.00}. so the service fee of {$4.00} was charged on the first business day of next statement cycle. '' I found this very surprising. For not even a second during the statement period of XXXX/XXXX/2016 to XXXX/XXXX/2016 was my balance in this account under {$500.00}. I had {$500.00} deposited and posted into my account on XXXX XXXX, 8 days before the start of the statement cycle. The only transactions during the statement cycle was a XXXX cent and XXXX cent deposit on the XXXX XXXX and later a XXXX cent withdrawal on XXXX XXXX. At no point during the statement cycle did the balance on my account dip below {$500.00} so I have no idea how Citibank calculated my average monthly balance to be " {$400.00}. '' I then called Citibank to clarify this matter on XXXX XXXX, and was connected to a Citibank supervisor " XXXX '' based in Texas. I spoke with her for almost an hour, and she was incredibly rude and unhelpful. When I complained to her about the irregularities in my account, she kept told me to refer to the terms and conditions. When I asked her to point out under where this {$4.00} charge would fall under in the Terms & Conditions for having an average monthly balance of over {$500.00} or how Citibank calculated my average monthly balance to be " {$400.00} '' she would leave me on hold for extended periods of time then tell me again to refer to the Terms & Conditions without explaining anything and eventually she hung up on my call. 
I believe Citibank may be committing widespread financial fraud by fraudulently charging fees on their consumers. They are incorrectly charging monthly fees in violation of their own terms of service, and then hiding this fee by not even showing it as a transaction in their online banking website and simply taking the money out of the account. I doubt I am the only person affected by this, and Citibank may be systematically defrauding millions of Americans like me which is why I 'm imploring the CFPB to thoroughly investigate this matter. I am more than happy to provide account statements or any other documentation necessary.