Product: Credit card or prepaid card

On XX/XX/XXXX I entered into a contract per XXXX XXXX in XXXX Tx for an amount of {$2400.00} to be paid to Synchrony Care Credit interest free for 2 years. This was my verbal understanding. 
I received initial documents from them, which I can now see quoted an expiration date of XX/XX/XXXX for the interest deferment. As I am a XXXX, who has had three XXXX  surgeries ( at that time I was XXXX, and had not yet had the XXXX  surgeries, so with greater impairment ), I still relied on my verbal understanding, since the print on the statement is too small for me to read. 
I set up autopayment in an amount that would have the debt paid off in the 2-year term I believed I was working with.

My contact with Synchrony has been by email which stated the expected balance each month and led me to believe I was on track to pay the full sum in a timely manner. 
After my XXXX payment I received the usual email, but this one stated a balance of double what I believed I owed. 

Upon logging into my account, I could only see the following : This was the weekend, and no customer service is available until regular business hours. I called first thing Monday morning and was told that my promotional offer had expired and I had been charged the above outrageous interest charge and that I should have seen a warning on my statement. 
The monthly email does NOT contain the statement or a link to it. If I use the link and log on I get this confusing screen that does not easily lead me to the statements. 


Having this screen which has statements in the smallest font at the bottom of the screen, virtually obscured by the View Credit Score box, its easy to see that I relied on the email and my understanding of the term and never drilled down on the statement. 
After instructions from the Customer Service employee, I found the statement and can see that there was a warning that the promotion was about to expire, but I would never have found it without said instruction and certainly never thought this was an urgent issue, since I was making no purchases and had no reason to think there was a problem. 
If the lender was interested in transparency, there should have been a warning on the monthly email that I would incur this interest charge after XX/XX/XXXX certainly on the XX/XX/XXXX email if no other. However, I believe it was their goal and design to hide the impending charge from me, so that they could hit me with a gotcha penalty, six months before the amount was fully paid. 
In my conversation with the bank, I was told that I should have asked them to send me a paper statement if I could not see the statement online, but again, I had no reason to believe that there was an issue. 
I immediately paid the reaming due {$600.00} from the original loan and am requesting that the interest charges be waived, or at least substantially reduced based on what I believe were deliberately deceptive practices to keep me unaware of the impending charge, therefore incurring an astronomical interest rate. 

Upon writing this, I have seen that there was a small additional amount over {$600.00}, so have paid an additional {$10.00} to cover. 

I should also mention that I have an excellent credit score ( over 800 ) and would never incur rates such as this. 
Did I make a mistake in not scouring each document, month by month? Yes, but I submit that a good faith institution would have communicated the danger openly, rather than hiding it under layers of fine print and difficult to locate documents. 
I believed Synchrony to be a reputable institution, having been led there by my doctor and having seen it elsewhere, and based my good faith actions on that trust. Unfortunately, that trust was misplaced, and they are merely another mob of opportunists, operating under cover of technical legality, while using tactics to assure them the greatest level of income without regard for whom they are robbing to get their questionable gains. 
Again my request here is to have the usurious interest charge removed I have fully paid my original balance, or at the very minimum to reduce it to a reasonable rate commiserate with my credit score.

Please let me know if there are addition actions or items needed to further this request. 
Sincerely, XXXX XXXX XXXX XXXX XXXX XXXX, XXXX TX XXXX XXXX