Product: Credit card or prepaid card

On XX/XX/XXXX I went to Bank of America branch in TX to take advantage of advertised promotional offer which was displayed on my credit card home page. It said get a 0 % APR for 1 year on transfers into my bank acct from my credit card. The total credit line was {$20000.00}. I had a balance of about {$12000.00} and available credit of {$8000.00}. I took the promotional offer and transferred the {$7700.00} at 0 % APR into my checking acct which I needed to complete a backyard project. I signed a little piece of document at the bank which I plan to attach and the guy at the bank said, XXXX XXXX, this is a great deal because you do n't have to worry about interest on the {$7700.00} as you would just focus on paying off the {$12000.00} because you have reprieve for one year on this one - " this one '' meaning the amount I just transferred to my bank checking account. I was very excited and  I left. I got Monthly Minimum Payments from XX/XX/XXXX - XX/XX/XXXX for {$410.00} which I paid on time for {$410.00} and my assumption was that interest charged on purchases within that period was part of that {$410.00} so I was happy to pay it. By the way interest charged on purchases within that period was {$210.00}. Next Payment XX/XX/XXXX - XX/XX/XXXX for {$400.00}. I was happy to pay it as well thinking interest charged on purchases was included in the Monthly Minimum Payment. By the way interest charged on purchases for that period was {$210.00} which is basically interest charged on outstanding balance. Next Payment XX/XX/XXXX - XX/XX/XXXX for {$420.00}. Which I will be paying in a week. I Interest charged on purchases for that period is {$220.00}. I later called them to ask how my Monthly Minimum Payment was being calculated and they said my Monthly Minimum Payment only applies towards the {$7700.00} that I transferred into my checking account and interest charges on purchases are basically capitalized so I am paying interest on interest every month. I told them that is illegal because a monthly minimum payment on a credit card must include interest payment for the period and they said no it was the responsibility that I took upon myself since I signed on to the promotion. My question is, how is it my responsibility to calculate how much interest I incur on purchases every month and add it to interest on previous balance then plan to pay it above whatever the bank dictates my Minimum Statement is based on the {$7700.00} I transferred. This does not make any logical sense and {$410.00} every month is a lot to pay on a 0 % APR card, just towards the principal. I called Bank of America and told them this smells like Fraud and the representative did not deny it only that he said I signed up for it. I decided to call XXXX XXXX and asked them what their opinion was on the issue and they said monthly Interest payment must be added into a Monthly Minimum Payment. Bank of America is capitalizing the monthly interest and making it difficult for me to make payments on the higher outstanding balance of {$12000.00} ( with Higher APR ) by keeping my Monthly Minimum Payment on the 0 % APR close to {$500.00} a month. They know that it would be difficult for me to make such a high monthly payment ( {$500.00} ) and still be able to pay towards the outstanding balance with high APR. This is fraud of the highest order and the 0 % APR was the trap.