Banks give credit cards knowing the used will eventually incur interest and that is how they make their money. They hope you will miss a payment so they can fine you and credit cards are probably the highest interest money-borrowing schemes known today.
Many people can afford to pay just the interest and hardly put a dent in the principle. If this sound like you, then apply for another card, like one with 0% for six months and do a balance transfer. In this way you can pay toward your principle and have no interest payment, this saves you money right off the bat. By obtaining another card with the same features, you can transfer from your high interest card to the zero card and right away that big chunk of interest payment will go toward you balance instead.
Banks want you to be in debt so they do not advertise this feature. Now you know, so check your cards for the lowest interest rate and start moving your money around. Some cards now charge for transfers, but if you do the math you can still come out ahead.