Product: Credit card

CitiBk cr card calcs appear to be out of whack! For yrs I have pd my bal in full monthly, but when I used Citi 's no int for a yr program to transfer cr to pay another cr card bal, I took advantage XX/XX/2016 because although there was a small transfer fee, there was no interest for a yr. Any other purchases I would make, there would be no interest charges unless I did n't pay the additional credit charges for purchases, if any, in full monthly, along with more than the minimum amount toward the transfer amount monthly until I paid the $ XXXX bal transfer in full. But prior to the bal xfer, I had charged {$980.00} XX/XX/2016. Forgetting that I chrgd {$480.00} on the stmt end date, I only pd {$500.00} on the XX/XX/XXXX due date, thinking that I was paying the bal in full ; therefore, CitiBk chrgd me {$7.00}, rightfully so, based on 17.24 %. The next month, I paid {$500.00} as well, autopay on the due date, 2 days prior to the stmt end date, and although I also owed the transfer fee of {$120.00}, my stmt showed an interest charge nearly the same as the previous month with a {$480.00} balance, when the balance was now only {$130.00}. 
I called CitiBk and argued with them until I was blue in the face, and they did n't get what I was trying to tell them. After 6 months of arguing with them, finally XXXX representative said she saw what I was talking about, and gave me a {$10.00} credit last night. But, as the interest charge was based on a false balance, which had a domino effect for months to come, I called CitiBk again. I was advised by the next representative that the computers are accurate and there is an interest charge if the balance is not paid in full. I corrected him and stated that the interest charge will be calculated on only the remaining balance that is not paid in full, and he argued with me to the point I told him I was reporting the company to Consumer Affairs for inaccurate calculations if they are charging me on the full balance before payments. Then, on XX/XX/XXXX I paid {$180.00} on an amount owing of only {$60.00}, but CitiBk chrgd me {$1.00} int when I had a {$120.00} credit after the payment, which was applied toward the $ XXXX bal xfer. I inquired, then, about a {$.00} charge on the XX/XX/XXXX statement that was explained as a " minimum interest charge '' when I owed nothing but the interest free $ XXXX balance transfer ; yet the stmt said the bal subject to int rate was a measly {$1.00}, so apparently the rep saw how ridiculous to chrg {$.00} on only {$1.00} balance, which was not true anyway because I had a credit to be applied toward the $ XXXX bal xfer, but he gave me the {$.00} credit. Although I feel justified to receive {$10.00} credit on my account, I feel cheated because I feel that CitiBk accounting system does not use accurate accounting methods ; therefore, leaves a lot to be desired. I spent so much time to prove their system is cheating the public. {$10.00} each person adds up in the end. This method of accounting caused a domino effect on the original {$480.00} XX/XX/2016. 
Hopefully you may unravel the problem so other consumers do not fall prey to these banks and their computer accounting methods. 
Thank you. 
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