Product: Credit card or prepaid card

In XX/XX/XXXX, while shopping at a XXXX XXXX XXXX, I opened a Synchrony bank credit card in order to make a store purchase. I applied for a store specific credit promotion of 0 % interest until XX/XX/XXXX. I was aware the 0 % promotion ended in XX/XX/XXXX, however I did NOT know that this was a deferred interest credit card offer. Neither the store employee or credit card company shared or made this critical detail apparent or clear. 
I also was NOT warned in advance that all of the deferred interest would be charged as of XX/XX/XXXX. Not a single email was sent to me to warn me or make me aware of this looming fate. 
The last time I reviewed my statement was XX/XX/XXXX and saw that I had a balance of {$1900.00}. I was under the impression that an APR rate would kick in as of XX/XX/XXXX, but not that I would be responsible for a retroactive year 's worth of interest. I made the decision to leave the balance of {$1900.00} and not pay it in full, because I was closing on my first home on XX/XX/XXXX and wanted to hold on to any extra cash I had for use towards my home closing fees. 
In the months of XX/XX/XXXX and XX/XX/XXXX, I was closing on my first home, renovating and moving in to it. I DID NOT log in to my Synchrony account until XX/XX/XXXX to review my account details. After I logged in, I looked into the account and nearly had a heart attack when I saw an interest charge of over {$1000.00}. 
Synchrony DID NOT send clear and transparent warnings that there was deferred interest in the credit card or that the deferred interest was going to kick in on XX/XX/XXXX. IF I HAD KNOWN THIS WAS THE REALITY, I would have paid the {$1900.00} balance IN FULL before XX/XX/XXXX. 
When I logged in to review my statement on XX/XX/XXXX, I noticed the approx. {$1000.00} of interest charges and sent a secure message to Synchrony bank in order to resolve the discrepancy. 
Three days later they responded on XX/XX/XXXX and explained the deferred interest charge with the following language included : In addition to this email, a letter further explaining the expired promotional balance on your account will be sent to you in the mail. You should expect to receive the letter within the next 7-10 days. 

If I had not sent that message to Synchrony, I would have never received email communication or a letter in the mail explaining the deferred interest charge. 

Later in the month I followed up with a call to Synchrony Bank in order to resolve or settle the incredulous high interest charge. On the call, I was met by the most ruthless, rude, discourteous Account Manager. I would have listed her name here, but when I asked her for it she responded with " she doesn't have to provide her name to me. '' The Synchrony Bank Account Manager not only attacked me, but also in plain terms accused me of lacking responsibility and said it was my own fault for not reading the " fine print. '' She also said to me you never even logged into your account, so its not our fault this happened. This is untrue ; I did in fact log in in XX/XX/XXXX. The manager added that if I was responsible, I would have at least logged in to my account and not have to have met this fate. She also compared me with her own responsible behavior and how she definitely reads the fine print on all of her own personal credit card offers. If I worked for an untrustworthy bank like Synchrony, I would probably also be wary of ANY fine print and comb through 40 pages of it most meticulously. 
Its safe to say that I was speechless. My response to her was an incredulous : Are you fighting with me? And her response was Yes, Im fighting with you. 
In short, the lack of transparency and communication on behalf of Synchrony, and the unprofessionalism and offensive nature of their employee, proved to me that this credit offer was completely setup to dupe consumers. On the XX/XX/XXXX call, Synchronys staff person met me from the get-go with attacks and offensive behavior, which were unwarranted, unprofessional and excessive. This behavior convinced me that Synchrony Bank is intentionally masking critical credit card details and burying them deep in their terms and conditions, in order to deceive customers and gain earnings from consumer naivet. This duplicity is then followed up with a customer service employee who attacks like a pit-bull in order to scare off misled consumers from asking any more questions. 
I would like to resolve this issue, and I am unsure as to the best method or avenue in doing so. I have called Synchrony Bank again today and have asked for ANY type of resolution to this problem, and once again was met by unrelenting staff who can not provide me with a single solution. 
As of today, I have paid of my {$1900.00} balance in full. The deferred interest remains on the account and I kindly ask for some type of settlement or resolution.