<prompt> Human: I have a bank of America credit card, recently my interest free promo ended and to my surprise 3000 dollars was added to my card. When I asked why they told me it was the interest from the promo year. Apparently interest free means postponed interest. My bill went from 120 a month to 270 and at some pretty bad timing. Is there anything I can do? How is this deceitful stuff even legal?  <response>: They back date the interest to the time you make the purchase, surprise! Some of the 0 interest offers do that, you have to read the terms. 