Your situation should be like this. After your bill was issued, you chose installment, so the problem came. The first installment fee is included in next month's bill, so the problem comes. You should have paid it back last month, but you didn't, because the installment fee of last month is included in next month's bill, that is to say, even if you don't spend money next month, there will still be tens of dollars of installment fee as your bill amount.