Product: Credit card or prepaid card

I have a CareCredit card ( through Synchrony Bank ) to pay for braces at a cost of roughly {$3400.00}. That is the only purchase on the card and will be the only purchase. According to the terms of the card, the payment will be {$160.00} per month over the 24 month period until the {$3400.00} promotional balance is paid. Each month I pay down the minimum as agreed. I know that the deferred interest is showing up on the statement, but what I did not recognize until a few months in was that instead of crediting my promotional balance by {$160.00} each month, they were only crediting {$130.00} each month towards the promotional balance. 

This means that their system shows my promotional balance as being {$28.00} too high after each payment. 

I was able to get this fixed for a previous month, so I tried paying double the monthly payment one month to see what would happen. Instead of seeing my promotional balance dropping by {$330.00}, my promotional balance again was only reduced by {$130.00}. 

It appears that no matter how much I was paying, they would only reduce my promotional balance by a set amount less than what I was paying. 

In this last complaint, I received the statement : " We are unable to setup automatic allocations of payments. We must be notified each month regarding your preference on how a payment should be allocated. Once your payment has posted to your account you may contact us at Customer Service or via the Online Messaging Center and we will be happy to apply your payment as requested. If you would like your payments to be reallocated, please respond to this message detailing how you would like each payment allocated. '' I find this completely unacceptable and not only deceptive, but fraudulent. When anyone agrees to pay the minimum as agreed to avoid deferred interest, the understanding is that the payment of this amount over the 24 month period ( or other period if no interest / interest waived with successful payments ) would result in a balance at the end of the 24 month period of {$0.00}. 

The following info shows the result of what is happening : Initial charge : $ 3340 Monthly minimum {$160.00} ( should pay it off in 20 months ) Monthly application to promo balance {$130.00} ( makes it take 24 months ) Total to be paid by the consumer if they do not catch this fraudulent practice {$4000.00} Over 2 years, this results in an extra {$670.00} paid ( or 20 % of the initial charge ). So in essence, paying off a " 0 % if paid in full over 24 months '' promo will result in a net hidden charge of 10 % each year IF the consumer can't do the math on their own to see what Synchrony is doing. 

If Synchrony is doing this with me, and I am being told as a consumer I need to individually reach out to them to try to get it applied correctly against the promotional balance using the basic everyday language of the agreement, then meaning of the agreement, then how many thousands of other customers are they essentially giving " 0 % deferred cards '' but in essence charging them 10 % in hidden math. 

Thank you for the venue to submit this complaint. It is entirely unacceptable that they are doing this not only to me but to countless others.