I was almost finished paying off my account that had a special intro rate of 0% interest, when I got my final statement. It said I was past due and it hit me with back interest on the full loan amount. In order to confirm that I wasn't past due they needed a transaction # for my last payment paid online, which I had not been saving.
Avoid doing any business with this company. If you need to, make sure you keep a record of every transaction that you do with them in regards to payments. They will try to find any way of screwing you to get their rediculous 400% effective APR.
