Product: Credit card or prepaid card

Recently, I needed to pay for school tuition and I didnt have enough cash to pay for it upfront, which is why I signed up for a credit card to pay the tuition and I went to look for XXXX  offered by an American bank on their website to find a card with 0 % intro APR offer so that I could pay off my tuition overtime, interest-free. I chose a bank where I was already customer card for this and didnt go to another bank. This card was advertised with {$200.00} bonus and 0 % intro APR for the first 15-months following account opening. After receiving the physical card, I paid my tuition, used the card thinking that there was no interest on card payments. 
After the first payment was due and I paid the minimum payment, then I saw a charge for interest fee by the bank. I called the bank and asked about this on Thursday XXXX, XXXX XXXX. The first answer I received over the phone was that there was no promotion on the card. I believed the representative, but I couldnt believe that I would apply for this card when there was no promotion, that is 0 % APR. That was the only reason I applied for the card. I looked up this credit card when I was still on the call with the representative, and it was promoted with {$200.00} cash back and 0 % APR. I told the representative what I was seeing on their web page. Following this, she said that there is a promotion now, but there wasnt one when I applied for the card back in XXXX. We finished that call with her stating that she opened a case looking into this. They also said I should have received a welcome letter with this information when I first got approved, but I could not find such an email. 
On Saturday XX/XX/XXXX, I called again to follow up. Again, they said that there was not a promotion when I applied for the card. I insisted that there was one and that was the only reason I applied for it. Following this, they changed their rhetoric and told me that there was a promotion but I wasnt approved for the promotion. Then I told them there was no statement saying that this credit card does not come with the promotion but I had to be approved separately for the % 0 APR. You will see in the attachments that there is no such statement. They state that the card comes with a Welcome offer of 0 % APR. The representative on the phone insisted that this was stated, as you can see in the attachments, when I click on the special character for Rate & Fees that is placed next to the 0 % APR offer statement, it takes me to additional information where it repeats the same promise/agreement. Following this, they said they will look into this and then they came back to me saying that I was not approved for the 0 % APR and a notification was sent to me agreeing to this and they had a screenshot of this. I asked for the screenshot. They said they cant provide it but will open an investigation into this. I would like to point out here that the rhetoric from a Welcome email stating the terms of promotion was sent to me changed into a notification sent to me saying I wasnt approved for 0 % APR. 
I then asked for an email address for the management so I could write to them, but they only gave me a XXXX XXXX XXXX Texas. If I didnt tell you this was American Express XXXX a known brand, you would think that I was a victim of a fraud by some old-time scammer. This is concerning Amex XXXX XXXX Credit Card offered by American Express which I applied for and got approved in XX/XX/XXXX. This was clearly a false advertisement and they intentionally try different ways, changing their rhetoric to make this my fault.