I purchased items on a Best Buy credit card through Citi Bank. I paid my bill before the due date on the first of every month. Eventually those payments began being applied to the previous month and I was charged late fees. Essentially according to Citi I was doubling up on payments. I called and they agreed with what I was saying and removed XXXX of the XXXX late fees. They said they can only remove so many in a year. They then advised me to pay the minimum due, which was higher than normal because of the late fee. They also told me to wait until at least the second of the month which I did. I paid in XXXX on the XXXX per their advice and it still got applied to the previous month XXXX XXXX XXXX. I called and they still gave the same excuse. 
