Synchrony Financial Credit Card Complaint

Synchrony Financial Credit card department,

APR or interest rate Ohio

There was a fee on my Amazon store account through Synchronicity Bank that should not have been there. They are promoting a 6 month interest free payment plan, however I purchased something outside of that promotion, and then made a payment, they did not apply the credit to the non-promotional balance, thus fees started to incur. I contacted them and I assume the funds have been properly reallocated so I will no longer incur fees while the promotional balance is paid off. However, I believe they are in violation of the law by not applying payments to higher interest purchases first. I just want to make this aware to CFPB so they can remedy any illegal actions by this bank and protect other consumers that might not be aware. Thank you.