Synchrony Financial Credit Card Complaint

Synchrony Financial Credit card department,

Billing statement Florida

I have a credit card called Care credit. It is a credit card that has no interest if you pay off your promotional balance within a said amount of time. I would only assume that all my payments would go to pay off the oldest balance. However I found this not to be a true statement when I was charged an absorbance amount for interest. I called to see what they balance had not been paid down and or off and they stated that I must call in each month and allocate where I want my payments to be placed. Ive never heard of such a practice. I called and demanded that they credit the payments I 've made since -/-/2015 to the latest running balance and was told they could only allocate for the last 6 months there for im being charged - in interest.