Synchrony Bank Credit Card Complaint

Synchrony Bank Credit card department,

Other fee Arizona

I have promotional ( no interest for 6 months ) balances on a Care Credit card. I have paid extra to be sure that the non-promotional balances ( $120.00 from -/-/2015 ) was paid in full. However, I have been accruing a 'minimum interest charge ' for the non-promotional balance for the last couple months. I did a chat with a representative from the company who reports they applied my payments as required by law. The law states that the highest interest rate needs to be paid off first - all of my charges are at the same interest rate, only the non-promotional charge is actually accruing interest at this time, so it appears my payments should have been applied there first. The representative with whom I chatted reports that she changed the way previous payment ( s ) were applied, but no charges were reversed. I would like to see the charges reversed, if possible, and for the company to not to this to anyone else.