Product: Credit card or prepaid card

I applied for a Citi Double Cashback Credit Card in XX/XX/2020. Did a balance transfer for {$2600.00} from my XXXX Cashback Credit Card. The balance is subject to a promotional rate at 0 % interest for 18 months. The balance was subject to a 3 % balance transfer fee. The total of the balance transfer fee was {$78.00}. 

I paid the balance transfer fee which kept my balance at {$2600.00} for my first statement, XX/XX/2020 statement. 

Since then I have had issues with interest being charged and incorrect statements. 

The second statement, for XX/XX/2020, I submitted a payment for each purchase, while the purchase was pending. The total of my purchases was {$140.00}. I paid that plus an additional {$320.00}. Here, my payments were not correctly credited, and after speaking to a representative, she stated that it was due to paying early, so the system did not recognize my XXXX payment as being intended for the balance transfer, and apparently the {$35.00} minimum payment was taken from that as well. Thus, the representative stated to pay an additional {$40.00} and she would credit me {$20.00}. I then received a {$20.00} to resolve the issue. 

In the third statement, for XX/XX/2020, I received XXXX cents in interest. My total charges on my purchases were {$180.00}. I made an additional {$150.00} payment to bring my balance transfer balance to {$2100.00} from the previous $ XXXX statement incorrectly stated that {$42.00} in purchases were subject to interest. I talked to an account manager and after going through my purchases, confirmed that I should not have been charged interest and credited the XXXX cents. I was informed that this would not occur again. I was also informed that in the future, the payment goes to the minimum payment first ( {$35.00} ), then the highest interest rate ( purchases at 16.99 % ), then the lowest interest rate ( balance transfer at 0 % ). Thus, I should wait until purchases post, pay an additional {$35.00} dollars on top of my purchases, then make my additional payment to the balance transfer after those payments post. 

I followed the managers advice. For my XXXX through XXXX purchases, I made a total of {$1400.00} in purchases. I received {$6.00} in credit for a return, XXXX cents in credit for a return, and the XXXX cents for the interest credit. Thus, XXXX plus {$35.00} equaled XXXX, minus the previously mentioned credits and my payment came to {$1400.00}. Then I made an additional payment on XX/XX/2020. Because I made an additional {$35.00} payment to go towards the minimum, I subtracted XXXX from XXXX and got {$110.00}, which I paid on this date. This brought my balance transfer amount to XXXX. I called Citi and spoke to a representative that assured me everything was paid correctly and there was no interest while rushing me off the phone. 

Today, XX/XX/2020, I received my XXXX statement showing that I was charged {$4.00} in interest on XXXX in purchases. 

I called CitiBank credit card line around XXXX XXXX EST. From there, I spoke with several representatives, was hung up by one, and ended a call with a final one at XXXX pm EST. Each representative had a different explanation. One stated I owed XXXX in purchases, another stated I had a balance of {$78.00}, another stated I had a balance of {$200.00}, to another stated that its only {$4.00} and that I shouldnt be so upset about that amount as its not a big deal. 
The final representative credited me the {$4.00} in interest but explained that despite being told by other representatives and my knowledge of how a credit card works, Citi does things differently. 

The representative stated that even though my balance transfer is subject to a 0 % interest rate, and I pay off my purchases in full before the statement closing date, I will still be subject to interest because the balance transfer and my total purchases are added together. As a result, I will have a statement balance that includes both the paid purchases and balance transfer amount. Thus, he said I should not use the card for purchases, because I will always be charged interest, despite the charges being paid off, because I used the credit card. He stated if I only paid down the balance transfer amount, then I would not be subject to interest. 

The representatives statement makes zero sense, and after asking him why no other representative explained this, he stated that hes telling me now for the future. I asked him to notate the account of our conversation. I am writing to : ( 1 ) Have my XXXX statement corrected from the XXXX amount to XXXX that is should reflect, ( 2 ) Have my credit report updated to reflect the XXXX statement amount, ( 3 ) Have the {$7.00} in purchases for cashback properly calculated in my cashback total.