Synchrony Financial Credit Card Complaint

Synchrony Financial Credit card department,

Credit card protection / Debt protection Pennsylvania

I have an account with synchrony bank for my - account all of my previous purchases had promotional periods on the last one I had paid off the promotional payment, synchrony used a portion of that to apply it to my payment that month, I did not realize what they had done and did not make a payment, then I realized they were charging me a huge amount of money in interest I called then they put some of the money back but not all of it and they refused to fix the last amount and are still charging me interest.