Product: Credit card

I had a promotional deferred interest balance on my Home Depot card. Home Depot 's online payment system allows you to select balances to apply your payments to. 

On XX/XX/XXXX I removed the promotional balance selected, which should have applied the payment to the revolving interest bearing balance. 
On XX/XX/XXXX I made a payment of {$200.00}. The payment was still applied to the promotional balance as it was expiring at the end of XXXX. 
On XX/XX/XXXX I called regarding a damaged item and tried to change the payment to apply it to the revolving balance. The representative stated the system would not allow this because the promotion was ending within 60 days and all payments must be applied to the promotional balance. 
On XX/XX/XXXX I selected the promotional balance and made a payment to the promotional balance, which the system showed was applied as I intended. 
On XX/XX/XXXX I paid the remaining promotional balance. 
On XX/XX/XXXX I confirmed that the promotional balance showed {$0.00} and removed the promotional balance selection so future payments would be applied to the revolving balance. 
On XX/XX/XXXX I made a payment of {$200.00} toward the revolving balance. 
On XX/XX/XXXX I confirmed the revolving balance and promotional balance showed {$0.00} and changed my selection to apply payments to a XXXX deferred interest promotion. 

When I got my statement it showed the deferred interest being assed with about a {$200.00} balance on my promotional ( now expired ) balance. My revolving balance was unpaid and XXXX XXXX promotional balance was paid off and another XXXX balance was partially paid. I called Home Depot, explained the issue, and was told I needed to pay my bill. I informed the first caller that Home Depot was in violation of XXXX XXXX XXXX for not applying my payments as offered by them and selected by myself and for not applying payments to the expiring balance, which the representative told me in XXXX was required. I requested a supervisor and explained the same information. The supervisor did not have an answer as to why the system applied the payments differently when the statement was issued. I was credited the interest charged ( over {$3000.00} ) and was told my complaint would be escalated for review. I told the supervisor I wanted an answer as to why their system is violating the XXXX and direction for call center staff to escalate issues instead of simply telling customers to pay their bills. After a few weeks, I received a letter from XXXX XXXXHome Depot that simply started they reviewed my complaint and found no evidence of discrimination. My complaint didn't mention discrimination at all, it was regarding illegal practices. During the call I informed Home Depot that I would be reporting the incident if they did not address the issue as XXXX XXXX  and Home Depot have a history of dishonest practices and have been sued regarding their promotional programs. It's clear they have no interest in changing and I'm concerned many other customers don't call to correct these issues and if they do, they may not be forceful enough to have the issues corrected. I can't imagine how many thousands of dollars they have received because they are not applying their payments and promotions correctly. I also had two previous promotional balance that were applied with different terms, which was corrected when I called after reviewing my statement. But, how many costumers do not review the statement and assume the agreement they entered into would just be reflected correctly on their accounts?