depending on your creditor, you may get hit with a "default rate" this means your interest rate will shoot through the F'n roof. 25-33% is not uncommon. You do not have to be 30 days late to get hit with this. It should not show up on your credit report, as you were not a full 30 days late. No need to contact them until you see the APR on your next bill, they won't work with you anyway. Once it goes up, it will not come down. If they hit you with that rate, the best thing you can do is get another, low interest card, and transfer the balance, then close the original card.