Synchrony Bank Credit Card Complaint

Synchrony Bank Credit card department,

Payoff process New York

I bought an air condition from - - 2 years ago by their credit card controlledby synchrony bank finance and then the bank added the interest of $830.00 for abalance of $490.00 without any alerts or warnings also I been - that timeI have an approve for that, so I tried to call the bank too many times to pay the balance and waive the interest but they refuse and take my phone number to call me backbut never happen