Product: Credit card or prepaid card

Greetings. This complaint is regarding a Home Depot credit card which is through Citibank. As a part of the revolving line of credit we are frequently given " promotional offers ''. The promotional offer in question was for a purchase in excess of {$290.00} and there would be no minimum payment due and no interest due if paid in full by the end of 18 months. This promotional period ends XX/XX/XXXX. The details are that we make the minimum payment for the revolving line of credit and for any payments made in excess of that, I request the monies be applied to a specific " promotional balance ''. On a regular basis, the amount I am paying toward a promotional balance is applied to the revolving line. Three payments from this situation that were not applied to the balance I denoted are : {$200.00} paid XX/XX/XXXX, {$200.00} paid XX/XX/XXXX ( together with the revolving payment of {$86.00} ), and {$440.00} paid XX/XX/XXXX. The promotional balance due XX/XX/XXXX has been paid in full but Citi misappropriates my payments. I have spoken with multiple reps from Citibank ( specifically XX/XX/XXXX and XX/XX/XXXX ) who have told me that I correctly processed my payments and directed the monies to the promotional balance. The monies are RE-DIRECTED by the bank from the promotional balance to the revolving line because I made my online payments near the end of the billing cycle. They admit that the system glitch is theirs but continue to " miss '' apply payments and require me to be in contact with them ( 6 times thus far ) for correction. In writing, I have been advised twice that the payments were correctly applied. I have been advised during two calls that the payments were applied correctly. I have spoken with three of their reps ( most recently : today a " management team representative '' who after researching the issue finally agreed they misapplied my payments. I told him that we have this happen often ( the XX/XX/XXXX payment has still not been correctly applied ) and he sarcastically said their system is not perfect ... My complaint is that if they are applying monies to the revolving live and not the promotional balances designated, the promotional balances will not be paid in full on time and interest will be due. Is this a scam so they can charge interest? If their system is known to make posting errors, why am I not contacted and asked how I intended to apply my payment- Oh, they do not need to ask me how I wanted the monies applied because my transaction is online in their system. As I have made no mistakes in making my payments, I should not have to continually ask for correction that does not happen, right? If in their payments log, it would show to which account the payment was applied, customers would have a better chance of catching their errors more quickly, or maybe they could just apply payments as I designate them. I am very thankful that I can find assistance for this through the government. Please contact me if anything further is needed. This account in in the name of XXXX XXXX XXXX and was opened in XXXX, We reside in Texas. Many thanks to all who review, reply or act on this request. XXXX, XXXX and XXXX XXXX