Product: Credit card or prepaid card

I am lodging a complaint against American Express for deceptive practices that triggered an additional {$250.00} interest charges that I would like them to rescind. 
I am planning to travel to Colorado in XXXX and noticed that I could get a {$200.00} statement credit if I used American Express travel services and prepaid for my hotel. In early XXXX, I charged a stay at XXXX XXXX XXXX, charging {$1100.00} to my AmEx card ( last fouXXXX XXXX ). 

I called as soon as I saw the next months statement. That {$1100.00} was considered immediately due and was part of my minimum payment of {$1200.00} minimum payment due no later than XX/XX/XXXX. This contrasts with the {$100.00} minimum payment that I made in XXXX. Equally concerning is the statement included a late payment warning that said if I did not make the minimum payment by XX/XX/XXXX, I would be charged a {$40.00} late fee and my XXXX XXXX XXXXe interest rate would be increased to 29.99 %. 
I called customer care ( XXXX ) and explained my dilemma. I did not know the {$1100.00} would be due immediately. I thought it would be rolled into my XXXX XXXX XXXXe balance and I would pay it over time, as the name implies. 

Since I still had {$1100.00} in my available XXXX XXXX XXXX limit, I was advised to select that XXXX XXXX XXXX transaction and designate it XXXX XXXX XXXX  My XXXX payment of {$250.00} would first be applied to any remaining pay in full balance then would be applied to XXXX XXXX XXXX. The customer service rep asked for my email address, and after the call ended he emailed me XXXX XXXX XXXX FAQs. 

On XX/XX/XXXX, I logged into my account to make the payment that is due on XX/XX/XXXX. After some digging, I found the XXXX XXXX XXXX transaction. Unfortunately, it was marked ineligible for XXXX XXXX XXXX. I contacted customer service again, this time via chat. Heres that transcript. 

Today XXXX XXXX, please select one of these options, or in a few words tell me what you need help with. 
XXXX PM Good evening. I called when I received my last credit card statement. 
XXXX PM Here are some things I can help you with : XXXX PM I made a travel reservation through AmEx and paid for the room in advance on my card in order to get a {$200.00} statement credit. 
XXXX PM A Customer Care Professional will be with you in about two minutes. In the meantime, please provide any information that may help us assist you. 
XXXX PM I do not see that {$200.00} statement credit, and the {$1200.00} transaction is marked as my new minimum payment. 
XXXX PM The customer service rep I spoke with weeks ago said I could apply $ XXXX toward my pay over time balance. My {$250.00} payment would then be applied toward pay in full then pay over time. 
XXXX PM I logged in tonight to make that change, but the only option I am given is a payment plan, which tacks on a mandatory interest charge. This is bait and switch. 
XXXX PM Hello, XXXX. 
XXXX PM How do I apply $ XXXX toward my pay over time balance as I was told earlier? 
XXXX PM I read your chat reason and let me quickly review your account details. 
XXXX PM Could you confirm the charge amount you made for the hotel credit? By that time I will also check the detail on pay over time. 
XXXX PM XXXX XXXX PM The AmEx website wants to log me off for lack of activity XXXX PM Thank you for waiting patiently, I checked your account and firstly to address your pay over time query, The amount which you are XXXX is the pay in full section balance. This balance includes all the charges which is not pay over time which included the charges you have been revolving from previous statement. 

XXXX PM When you make the payment the payment is first adjusted with your pay in full balance and then with pay over time balance. 
XXXX PM The previous agent, who said he noted our conversation, apparently lied. 
XXXX PM May I ask if you were told via chat or phone? 
XXXX PM I will file a complaint with federal authorities. Good evening XXXX PM The only option open to me was Plan It. So, I marked it Plan It and made my {$250.00} payment, as expected. 

These names are euphemisms. Plan It actually means plan to pay mandatory fees. That transaction is now deemed payable over 24 months with a monthly payment amount that American Express sets with mandatory fees of {$270.00} baked in. The mandatory fee wipes out the value of the {$200.00} statement credit I was trying to get by booking through XXXX XXXXs XXXX XXXX.