Product: Credit card or prepaid card

I am a customer of Synchrony Bank XXXX Care Credit. Recently my account changed from a Care Credit charge card to a Care Credit Rewards Master Card. This was not a change that I requested. Due to the change and subsequent confusion regarding which app or website to use to make a payment as well as personal infirmity, I missed a payment that was due on XX/XX/XXXX. On XX/XX/XXXX I received a call from Synchronys automatic payment reminder system. At that time, I opted to use my XXXX debit card to make a {$200.00} payment to my account ( the minimum due was {$54.00} ). I received a confirmation number for my payment and immediately saw the transaction as pending in my checking account. 

A week later I received another call, as well as an email, reminding me to make a payment towards my account. Having just made a payment, this alarmed me. I logged into my account and saw a charge for a late fee, but no evidence of my payment of {$200.00}. I looked at my checking account and found that the {$200.00} transaction had been debited from my account on XX/XX/XXXX. From there, I contacted customer service for Synchrony. I explained the situation from my perspective and why I was concerned. I was advised that the payment had been processed, but not posted to my account. They offered to file a dispute on my behalf. The agent could not tel me where my payment was, nor any other information. I was assured that this is the first time this has happened and that they would file a dispute. I maintained then, as I do now, that the only thing in dispute is what Synchrony has done with my payment. I escalated my call to a supervisor who repeated that the payment had been processed but not posted and that a dispute would be filed on my behalf. They offered no further explanation but assured me that the payment just needed to be posted to my account. I was advised to wait XXXX hours to see the payment post. 

On Monday, XX/XX/XXXX I looked at my account to see if my payment had been posted. It had not. I submitted a message through the secure messaging system to follow up on the status of the payment. On XX/XX/XXXX I received a message back stating that they could not find evidence that the payment had been made and requested that I submit proof from my financial institution. 

I contacted customer service via phone again on XX/XX/XXXX and asked for a follow up. I was told again that they could see the {$200.00} payment but that it wasnt posted. Further inquiries into the matter resulted in obfuscation of information regarding my account, demands that I provide proof of the transaction, and overt coercion to make an additional payment while the dispute was pending. Again, I escalated the matter to a supervisor. The same information was repeated and demands made. 

I contacted my financial institution for the requested information. They advised that this was a straightforward debit card transaction that was fully processed. After consulting with an escalation team, the representative advised that the level of information requested by Synchrony for this type of transaction was onerous and suspicious. They provided me with all of the tracking information for the debit card payment and stated that the option of disputing the payment was available to me if I wished to exercise it. 

I have provided the information regarding the payment to Synchrony through their secure messaging system and am awaiting a reply. 

I want help, please, resolving this matter and holding Synchrony accountable for their gross mismanagement of my good faith payment.