We purchased full-house carpet from a reputable, well-known carpet company in Auburn California last year. We purchased it on a 90 days same as cash basis. The deal was, if we paid the entire balance due by December 12, which was apx. $9, 100.00, there would be no interest charges. I guess the store charged it with a "Citibank retail" credit card. We paid our entire balance, by check, along with our final invoice, by mail on December 1 or 2nd--plenty of time to be received and processed by the due date of Dec. 12, 2008. Citibank has been calling and harrassing us almost daily, ever since, claiming that the majority of our bill was actually due on December 5 because the Store billed THEM with two separate invoices on two separate days. We only ever received ONE invoice with ONE due date of Dec. 12, which we paid in full and ON TIME. We have our cleared payment through our Bank of America checking account that was processed on December 15. It takes 3-7 days for a payment to come through on a checking account statement, so clearly our entire balance was received by Citibank sometime between December 8 through December 12, at the latest. Citibank retail collection department calls us several times every day asking for the payment of the interest, which now totals nearly $1, 000.00 with the fees they have added on!!! None of this makes sense--why would be pay our entire balance of over $9, 000 on time, on or before the due date, and still have Citibank expect that we would pay the interest charges because they either delayed processing our payment when they received it, or have engaged in some sort of scam, claiming our bill was due one week prior to the due date shown on our invoice, so they could then claim we owed them all the back interest. What can we do besides file claim with the State Attorney General's office and the Federal Trade Commission?