Product: Credit card or prepaid card

I have a credit card with Walmart through Synchrony. My credit limit was {$1800.00}. On XX/XX/XXXX, I made an on-time payment of {$59.00} to Synchrony, leaving me with a balance of {$1700.00}. The due date was XX/XX/XXXX. On XX/XX/XXXX, I made a payment of {$1700.00} to pay off the credit card in full. Also on XX/XX/XXXX, after I made this payment, Synchrony added an interest charge of {$35.00}. As can be seen on the statement, this payment was recorded for the XXXX statement period, and there should have been nothing due for the XX/XX/XXXX payment. Instead, that interest payment should have been due for the XX/XX/XXXX payment. On XX/XX/XXXX, the statement date for XXXX, Synchrony declared my account past due and decreased my credit limit to {$200.00}. They claim that this was due to a random check to determine my credit worthiness. They claimed this was them doing their due diligence. They sent us a letter claiming that the reason for the decrease in the limit was due to serious delinquency ( although I have XXXX delinquent accounts on the Transunion report that they claimed to have used ) ; proportion of balances to credit limits ( despite this actually being better now than it was when they raised my credit limit in the past from {$200.00} XXXX ; revolving accounts are too high ( despite my accounts actually being higher when they raised my credit limit, and they are lower now and were even lower when they would have made the decision ) ; and number of accounts with delinquency ( despite the fact that I have had XXXX delinquencies on my account for the last 10 years or more ). As a result of this decrease in credit limit for no acceptable reason and due to no fault of my own, Synchrony has single-handedly reduced my credit score, coincidentally, as I paid off the credit balance owed to them. This is unfair and this is deceptive behavior on the part of Synchrony. <P/>We contacted Synchrony on XX/XX/XXXX, as soon as we became aware of the balance owed. They immediately offered to take off the interest payments, but they claimed they could do nothing about the credit limit. They said we must appeal to the credit agency that provided them with the report. The clear problem here is that when we appeal this to the credit agency, they will tell us that they do n't know why the bank decided our credit was no longer worthy of the higher limit. Both sides will essentially blame the other and be blameless themselves. We will achieve no result from either institution, but we will be injured greatly the next time we apply for any credit or loan in the future. This is completely unacceptable as it is unfair to the consumer. Plus, we do n't know yet if they have reported a delinquency despite not actually having a delinquency, since we paid off the entire balance on XX/XX/XXXX, which should have been considered for our XX/XX/XXXX payment, as it was indicated on our XXXX statement which is attached. <P/>Is this an underhanded way to discourage consumers from paying off their balances, so they continue to pay the high interest rates charged on high balances? Is this another way to nickle and dime hard working consumers who have worked hard to maintain decent credit scores? My wife and I have worked very hard to improve our credit score, and through no fault of our own, no delinquency, no faltering of payments, and with a much better financial situation, Synchrony has decided that my family shall suffer because we are no longer a slave to their high interest rates!